Cyclic quaternary ammonium salts as fuel or lubricant additives

ABSTRACT

Quaternary ammonium salts of formula: wherein each of R1 and R2 is independently selected from an optionally substituted alkyl, alkenyl or aryl group having less than 8 carbon atoms, R together with N forms an aliphatic or aromatic heterocycle having less than 12 carbons atoms and R5 is hydrogen or an optionally substituted hydrocarhyl group. The use of these compounds as fuel or lubricant additives, especially as diesel fuel additives,

The present invention relates to novel quaternary ammonium compounds, toa composition comprising such compounds and to methods and uses relatingthereto.

In particular the present invention relates to the use of quaternaryammonium compounds as fuel or lubricant additives, especially as fueladditives and preferably as diesel fuel additives.

It is common to include nitrogen-containing detergent compounds inlubricating oil and fuel oil compositions in order to improve theperformance of engines using such compositions. The inclusion ofdetergent additives prevents the fouling of moving parts of the engine.Without such additives fouling would cause the performance of the engineto diminish and eventually cease.

Many different types of quaternary ammonium salts are known in the artfor use as detergent additives in fuel and lubricating oil compositions.Examples of such compounds are described in U.S. Pat. Nos. 4,171,959 and7,951,211. One commonly used class of quaternary ammonium additives isprepared by the reaction of a tertiary amine with an epoxide and anacid. These compounds typically include a quaternised nitrogen atomincluding at least one hydrophobic group. The hydrophobic group isusually a hydrocarbyl chain having at least 8 carbon atoms. The mostcommonly used quaternary ammonium salt additives are based on compoundshaving a hydrocarbyl substantive with a molecular weight of at least 200and typically at least 500. Indeed many of these compounds include apolyisobutenyl substituent having an average molecular weight of 1000and sometimes higher.

The present inventors have surprisingly found that good deposit controlcan be achieved when using quaternary ammonium salt additives preparedfrom cyclic low molecular weight amines.

According to a first aspect of the present invention there is provided aquaternary ammonium salt of formula:

wherein each of R¹ and R² is independently selected from an optionallysubstituted alkyl, alkenyl or aryl group having less than 8 carbonatoms, R together with N forms an aliphatic or aromatic heterocyclehaving less than 12 carbon atoms and R⁵ is hydrogen or an optionallysubstituted hydrocarbyl group.

The quaternary ammonium salts of the present invention include cationsof formula R══N⁺R¹R², wherein each of R¹ and R² is independently anoptionally substituted alkyl, alkenyl or aryl group having less than 8carbon atoms, and R together with N forms a heterocycle having less than12 carbon atoms.

For the avoidance of doubt, the structure R══N⁺R¹R² is used to indicatethat the group R forms 2 bonds to N, not that it forms a double bond.

In this specification, unless otherwise stated references to optionallysubstituted alkyl groups may include aryl-substituted alkyl groups andreferences to optionally-substituted aryl groups may includealkyl-substituted or alkenyl-substituted aryl groups.

R¹ and R² may be the same or different. In some embodiments they are thesame. In some embodiments they are different.

Preferably R¹ is an optionally substituted alkyl, alkenyl or aryl grouphaving from 1 to 7 carbon atoms, preferably from 1 to 5 carbon atoms,more preferably from 1 to 4 carbon atoms.

R¹ may be optionally substituted with one or more groups selected fromhalo (especially chloro and fluoro), hydroxy, alkoxy, keto, acyl, cyano,mercapto, alkylmercapto, dialkylamino, nitro, nitroso, and sulphoxy. Thealkyl groups of these substituents may be further substituted.

Preferably R¹ is an optionally substituted alkyl or alkenyl group.Preferably R¹ is an optionally substituted alkyl group. Preferably R¹ isan optionally substituted alkyl or alkenyl group having from 1 to 7carbon atoms, preferably from 1 to 6 carbon atoms, more preferably from1 to 5 carbon atoms, suitably from 1 to 4 carbon atoms, preferably from1 to 3 carbon atoms, more preferably from 1 to 2 carbon atoms.

Preferably R¹ is an optionally substituted alkyl or alkenyl group,preferably having from 1 to 6, preferably from 1 to 4 carbon atoms.Preferably R¹ is an alkyl group. It may be a substituted alkyl group,for example a hydroxy substituted alkyl group. Preferably R¹ is anunsubstituted alkyl group or a hydroxy alkyl group. More Preferably R¹is an unsubstituted alkyl group. The alkyl chain may be straight-chainedor branched. Preferably R¹ is selected from methyl, ethyl, propyl andbutyl, including isomers thereof. Most preferably R¹ is methyl.

In some embodiments R¹, R and N together form an aromatic ring and thequaternary ammonium salt may have the structure:

In such embodiments the total number of carbon atoms in groups R and R¹is less than 19. An example of such a compound is a methyl pyridiniumsalt.

Preferably R² is an optionally substituted alkyl, alkenyl or aryl group,preferably having from 1 to 6, preferably from 1 to 4 carbon atoms.Preferably R² is an optionally substituted alkyl group. In somepreferred embodiments R² is a hydroxy substituted alkyl group. Mostpreferably R² is a 2-hydroxyalkyl group. Suitably R² is selected from2-hydroxyethyl, 2-hydroxypropyl 3-propoxy-2-hydroxy propyl and2-hydroxybutyl. In one especially preferred embodiment R² is2-hydroxybutyl. In one preferred embodiment R² is3-propoxy-2-hydroxypropyl.

In some preferred embodiments R² is an unsubstituted alkyl group. Thealkyl group may be straight chained or branched. Preferably R² isselected from methyl, ethyl, propyl and butyl, including isomersthereof. In one preferred embodiment R² is methyl.

The group R together with N forms a heterocycle having less than 12carbon atoms.

R together with N may form an aliphatic heterocyclic group or anaromatic heterocyclic group. Thus they form a heterocyclic ring. Theremay be one or more further heteroatoms in the ring. Suitably the ringmay include one or more further atoms selected from N, O and S.

The heterocyclic group formed by R and N may be substituted orunsubstituted; i.e. there may be one or more substituents bonded toatoms that form the ring. Suitable substituents include halo (especiallychloro and fluro); hydroxy, alkoxy, keto, acyl, cyano, mercapto,alkylmercapto, alkyl, alkenyl, aryl, dialkylamino, alkylamino, nitro,nitroso, and sulphoxy. The alkyl, alkenyl and aryl groups of thesesubstituents may be further substituted.

The heterocyclic group may be substituted with a further cyclic groupi.e. it may be part of a bicyclic heterocyclic group.

In some preferred embodiments the heterocyclic group formed by N and Ris not substituted.

Preferably the group formed by R and N is a heterocyclic group havingfrom 3 to 12 atoms in the ring. The atoms in the ring include carbonatoms and other atoms. Preferably the heterocyclic ring includes 3 to 10atoms, preferably 4 to 8, more preferably 5 to 7 atoms.

In some preferred embodiments the heterocyclic group contains onlycarbon and nitrogen atoms within the ring.

The heterocyclic group formed by R and N may be aliphatic or aromatic.

In some preferred embodiments R and N together form an aliphatic oraromatic heterocycle having 5 to 7 atoms in the ring.

Suitable aliphatic heterocyclic groups include those based onpyrrolidine, piperidine, morpholine and piperazine.

Suitable aliphatic heterocyclic groups include unsaturated heterocyclesthat are not aromatic. i.e. they may contain one or more double bonds,for example those based on dihydropyrrole,.

Suitable aromatic heterocyclic groups including those based on pyrrole,pyridine, imidazole, pyrimidine, isoxzole, quinolone, oxazole, andpyrazole.

In especially preferred embodiments R and N together form an imidazolemoiety or a pyrrolidine moiety.

Suitably R contains 3 to 11 carbon atoms (and optional heteroatoms withthe ring), preferably 3 to 10 carbon atoms, preferably 3 to 9 carbonatoms, suitably 3 to 8 carbon atoms, preferably 3 to 7 carbon atoms,more preferably 3 to 6 carbon atoms, for example 3 to 5 or 3 to 4 carbonatoms.

Preferably R contains less than 8 carbon atoms.

The anion of the quaternary ammonium salts of the present invention iscarboxylate group of formula R⁵COO—. This is suitably the residue of anacid of formula R⁵COOH. R⁵ may comprise one or more additional acid orester groups. It may be a monoacid, a diacid or a polyacid. It may be amonoester of a diacid or a partial ester of a polyacid. Thus R⁵ may be—R′H, —R′COO⁻, —R′COOH, —R′COOR″, R′(COOR″)_(n) wherein each R′ isindependently an optionally substituted hydrocarbyl group, each R″ mayindependently be H or an optionally substituted hydrocarbyl group and nis at least 1.

R⁵ may be hydrogen or an optionally substituted hydrocarbyl group.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbylgroup” is used in its ordinary sense, which is well-known to thoseskilled in the art. Specifically, it refers to a group having a carbonatom directly attached to the remainder of the molecule and havingpredominantly hydrocarbon character. Examples of hydrocarbyl groupsinclude:

(i) hydrocarbon groups, that is, aliphatic (which may be saturated orunsaturated, linear or branched, e.g., alkyl or alkenyl), alicyclic(e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic-,aliphatic-, and alicyclic-substituted aromatic substituents, as well ascyclic substituents wherein the ring is completed through anotherportion of the molecule (e.g., two substituents together form a ring);

(ii) substituted hydrocarbon groups, that is, substituents containingnon-hydrocarbon groups which, in the context of this invention, do notalter the predominantly hydrocarbon nature of the substituent (e.g.,halo (especially chloro and fluoro), hydroxy, alkoxy, keto, acyl, cyano,mercapto, alkylmercapto, amino, alkylamino, nitro, nitroso, andsulphoxy);

(iii) hetero substituents, that is, substituents which, while having apredominantly hydrocarbon character, in the context of this invention,contain other than carbon in a ring or chain otherwise composed ofcarbon atoms. Heteroatoms include sulphur, oxygen, nitrogen, andencompass substituents as pyridyl, furyl, thienyl and imidazolyl. Ingeneral, no more than two, preferably no more than one, non-hydrocarbonsubstituent will be present for every ten carbon atoms in thehydrocarbyl group; typically, there will be no non-hydrocarbonsubstituents in the hydrocarbyl group.

R⁵ is preferably selected from hydrogen and an optionally substitutedalkyl, alkenyl or aryl group.

In some embodiments R⁵ is an optionally substituted phenol residue. Forexample R⁵ may be a 2-hydroxyphenyl group.

In one embodiment R⁵ is COOR⁰ where R⁰ is a C₁ to C₄ alkyl group. In oneembodiment R⁵ is a 2-(methylcarboxy)-phenyl group.

Thus the anion R⁵COO— of the quaternary ammonium salt may be the residueof an ester of salicylic acid, oxalic acid or phthalic acid.

R⁵ may be hydrogen and the anion is a formic acid residue. In someembodiments R⁵ is a low molecular weight alkyl or alkenyl group having 1to 8, preferably 1 to 6, preferably 1 to 4, for example 1 or 2 carbonatoms. The alkyl or alkenyl group may be straight chain or branched.

The present inventors were very surprised to find that embodiments ofthe present invention in which R⁵ has less than 8 carbon atoms, forexample less than 5 carbon atoms, gave excellent deposit control inmodern diesel engines, since conventional wisdom would lead the skilledperson to believe that a deposit control additive must include along-chain hydrocarbyl group.

The anion R⁵COO— may be the residue of a monoacid, a diacid or apolyacid. It may be the residue of a monoester of a diacid or a partialester of a polyacid.

In some embodiments R⁵ is an optionally substituted C₆ to C₅₀ alkyl oralkenyl group, preferably a C₆ to C₄₀ alkyl or alkenyl group, morepreferably a C₈ to C₃₆ alkyl or alkenyl group, preferably a C₈ to C₃₀alkyl or alkenyl group, suitably a C₁₀ to C₂₄ alkyl or alkenyl group,for example a C₁₀ to C₂₀ alkyl or alkenyl group. The alkyl or alkenylgroup may be straight chain or branched.

In some embodiments R⁵COO— may be the residue of a diacid or a monoesterof a diacid, for example the residue of an optionally substitutedphthalic acid or succinic acid derivative. Some preferred species arehydrocarbyl substituted phthalic acid or succinic acid derivativeswherein the hydrocarbyl substituent has a molecular weight of from 100to 5000, preferably from 300 to 4000, suitably from 450 to 2500, forexample from 500 to 2000 or from 600 to 1500.

In some embodiments R⁵COO— may be the residue of a polyacid or a partialester of a polyacid, for example the residue of an optionallysubstituted pyromellitic acid derivative. Some preferred species arehydrocarbyl substituted pyromellitic acid derivatives wherein thehydrocarbyl substituent has a molecular weight of from 100 to 5000,preferably from 300 to 4000, suitably from 450 to 2500, for example from500 to 2000 or from 600 to 1500.

In some embodiments R⁵ is CHR¹¹CHR¹²COOR¹³ wherein each of R¹¹, R¹² andR¹³ is hydrogen or an optionally substituted hydrocarbyl group.Preferably one of R¹¹ and R¹² is hydrogen and the other is an optionallysubstituted hydrocarbyl group. In one embodiment the optionallysubstituted hydrocarbyl group is preferably a polyisobutenyl group,preferably having a molecular weight of from 100 to 5000, preferablyfrom 300 to 4000, suitably from 450 to 2500, for example from 500 to2000 or from 600 to 1500.

In one embodiment the hydrocarbyl group (R¹¹ or R¹²) is an alkyl oralkenyl group having 6 to 30 carbon atoms, preferably 10 to 26 carbonatoms, more preferably 12 to 24 carbon atoms, suitably 16 to 20 carbonatoms, for example 18 carbon atoms.

In one embodiment the hydrocarbyl group (R¹¹ or R¹²) is an alkyl oralkenyl group having 6 to 50 carbon atoms, preferably 12 to 40 carbonatoms, more preferably 18 to 36 carbon atoms, suitably 24 to 36 carbonatoms, for example 30 carbon atoms.

The skilled person will appreciate that commercial sources of acidsincluding hydrocarbyl chains often contain mixtures of homologues, inwhich minor amounts of alkyl chains having greater or fewer carbon atomsare also present.

In some embodiments R¹³ is hydrogen. In some embodiments R¹³ is anoptionally substituted alkyl group, preferably having 1 to 20 carbonatoms. Suitably R¹³ is an unsubstituted alkyl group, preferably having 1to 12 carbon atoms. In one embodiment R¹³ is a 2-ethyl hexyl group. Inanother embodiment R¹³ is methyl.

In one especially preferred embodiment R⁵ is methyl. In anotherespecially preferred embodiment R⁵ is a C₁₇ alkenyl group.

The quaternary ammonium compounds of the present invention may beprepared by any suitable method. Such methods are known to the personskilled in the art.

Suitably the quaternary ammonium salts of the present invention areprepared by the reaction of a tertiary amine of formula R══NR¹ with aquaternising agent. For the avoidance of doubt the structure “R══NR¹” isused to indicate that the group forms 2 bonds to N, not that it forms adouble bond.

The quaternary ammonium salts of the present invention may be preparedby reaction of a tertiary amine with a quaternising agent selected fromdialkyl sulfates, benzyl halides, hydrocarbyl substituted carbonates,alkyl halides, alkyl sulfonates, sultones, hydrocarbyl substitutedphosphates, hydrocarbyl substituted borates, alkyl nitrites, alkylnitrates, hydroxides, N-oxides or mixtures thereof, followed by an anionexchange reaction.

However in preferred embodiments the quaternary ammonium salt of thepresent invention is prepared by reacting a cyclic tertiary amine offormula R══NR¹ with a quaternising agent selected from:

-   -   (i) an ester of formula R⁵COOR²;    -   (ii) a carbonate compound of formula R⁴OCOOR² and then a        carboxylic acid of formula R⁵COOH; and    -   (iii) an epoxide having less than 8 carbon atoms and a        carboxylic acid of formula R5COOH;

wherein R, R¹, R², R⁵ are as defined herein and R⁴ is an optionallysubstituted hydrocarbyl group.

The present invention may thus provide a method of preparing aquaternary ammonium salt of the first aspect, the method comprisingreacting a cyclic tertiary amine of formula R══NR¹ with a quaternisingagent selected from:

-   -   (i) an ester of formula R⁵COOR²;    -   (ii) a carbonate compound of formula R⁴OCOOR² and then a        carboxylic acid of formula R⁵COOH; and    -   (iii) an epoxide having less than 8 carbon atoms and a        carboxylic acid of formula R⁵COOH;

wherein R, R¹, R², R⁵ are as defined herein and R⁴ is an optionallysubstituted hydrocarbyl group.

The compound of formula R══NR¹ is a cyclic tertiary amine. By this wemean to refer to an amine group in which the nitrogen atom is part of aheterocyclic ring and is preferably further bonded to another group.

Suitably the compound of formula R══NR¹ is a cyclic tertiary aminehaving less than 18 carbon atoms. Preferably it has less than 16 carbonatoms, suitably less than 14 carbon atoms, preferably less than 12carbon atoms, for example less than 10 carbon atoms, less than 8 carbonatoms or less than 6 carbon atoms.

Suitably the compound of formula R══NR¹ is an N-substituted heterocyclicamine. Preferably it is an N-alkyl heterocyclic amine having 5 to 7atoms in the heterocyclic ring.

In some preferred embodiments the tertiary amine is an N-methyl cyclicamine including a heterocyclic ring moiety may include one or morefurther heteroatoms such as O, N or S and may be aliphatic ornon-aromatic.

There are many different compounds of this type and these will be knownto the person skilled in the art.

Some suitable amines of formula R══NR¹ for use herein are based onN-alkyl heterocycles, for example N-methyl heterocycles, selected frompyrrolidine, piperidine, morpholine, piperazine, pyrrole, imidazole anddihydropyrrole. These compounds have the following structures:

Other suitable amines include those based on the above in which theheterocyclic ring includes one or more further alkyl, alkenyl or arylsubstituents, provided the total number of carbon atoms in the tertiaryamine is less than 19. For example compounds which include one, two orthree methyl groups bonded to carbon atoms within the heterocyclic ringare within the scope of the invention.

Some suitable amines of formula R══NR¹ for use herein are based onheterocycles in which R¹, R and N together form an aromatic ring, forexample those based on piperidine, pyrimidine, isoxazole and oxazole.

Other suitable amines include those based on the above in which theheterocyclic ring includes one or more further alkyl, alkenyl or arylsubstituents, provided the total number of carbon atoms in the tertiaryamine is less than 19.

Examples of suitable amines of formula R══NR¹ for use in preparing thequaternary ammonium salts include a 1-methyl pyrrolidine,1,2-dimethylpyrrolidine, 1,3-dimethylpyrrolidine,1,2,3-trimethylpyrrolidine, 1,2,4-trimethylpyrrolidine,1,2,5-trimethylpyrrolidine, 1,3,4-trimethylpyrrolidine,1,2,3,4-tetramethylpyrrolidine, 1,2,3,5-tetramethylpyrrolidine,2-ethyl-1-methylpyrrolidine, 3-ethyl-1-methylpyrrolidine,2-ethyl-1,3-dimethylpyrrolidine, 2-ethyl-1,4-dimethylpyrrolidine,2-ethyl-1,5-dimethylpyrrolidine, 3-ethyl-1,2-dimethylpyrrolidine,3-ethyl-1,4-dimethylpyrrolidine, 4-ethyl-1,2-dimethylpyrrolidine,1-methyl-2-propylpyrrolidine, 1-methyl-3-propylpyrrolidine,2-isopropyl-1-methylpyrrolidine and 3-isopropyl-1-methylpyrrolidine,1-methylpiperidine, 1,2-dimethylpiperidine, 1,3-dimethylpiperidine,1,4-dimethylpiperidine, 1,2,3-trimethylpiperidine,1,2,4-trimethylpiperidine, 1,2,5-trimethylpiperidine,1,2,6-trimethylpiperidine, 2-ethyl-1-methylpiperidine,3-ethyl-1-methylpiperidine, 4-ethyl-1-methylpiperidine, 4-methylmorpholine, 2,4-dimethylmorpholine, 3,4-dimethylmorpholine,2,3,4-trimethylmorpholine, 2,4,5-trimethylmorpholine,2,4,6-trimethylmorpholine, 3,4,5-trimethylmorpholine,2-ethyl-4-methylmorpholine, 3-ethyl-4-methylmorpholine,1,4-dimethylpiperazine, 1,2,4-trimethylpiperazine,1,2,3,4-tetramethylpiperazine, 1,2,4,6-tetramethylpiperazine,1-methyl-1H-pyrrole, 1,2-dimethyl-1H-pyrrole, 1,3-dimethyl-1H-pyrrole,1,2,3-trimethyl-1H-pyrrole, 1,2,4-trimethyl-1H-pyrrole,1,2,5-trimethyl-1H-pyrrole, 1,3,4-trimethyl-1H-pyrrole,1,2,3,4-tetramethyl-1H-pyrrole, 1,2,3,5-tetramethyl-1H-pyrrole,1-methyl-2,3-dihydro-1H-pyrrole, 1,5-dimethyl-2,3-dihydro-1H-pyrrole,1,4-dimethyl-2,3-dihydro-1H-pyrrole,1,3-dimethyl-2,3-dihydro-1H-pyrrole,1,2-dimethyl-2,3-dihydro-1H-pyrrole,1,4,5-trimethyl-2,3-dihydro-1H-pyrrole,1,3,5-trimethyl-2,3-dihydro-1H-pyrrole,1,2,5-trimethyl-2,3-dihydro-1H-pyrrole,1,3,4-trimethyl-2,3-dihydro-1H-pyrrole,1,2,4-trimethyl-2,3-dihydro-1H-pyrrole,1,2,3-trimethyl-2,3-dihydro-1H-pyrrole,1,3,4,5-tetramethyl-2,3-dihydro-1H-pyrrole,1,2,4,5-tetramethyl-2,3-dihydro-1H-pyrrole,1,2,3,5-tetramethyl-2,3-dihydro-1H-pyrrole,1,2,3,4-tetramethyl-2,3-dihydro-1H-pyrrole,5-ethyl-1-methyl-2,3-dihydro-1H-pyrrole,4-ethyl-1-methyl-2,3-dihydro-1H-pyrrole,3-ethyl-1-methyl-2,3-dihydro-1H-pyrrole,2-ethyl-1-methyl-2,3-dihydro-1H-pyrrole,5-ethyl-1,4-dimethyl-2,3-dihydro-1H-pyrrole,5-ethyl-1,3-dimethyl-2,3-dihydro-1H-pyrrole,5-ethyl-1,2-dimethyl-2,3-dihydro-1H-pyrrole,4-ethyl-1,5-dimethyl-2,3-dihydro-1H-pyrrole,4-ethyl-1,3-dimethyl-2,3-dihydro-1H-pyrrole,4-ethyl-1,2-dimethyl-2,3-dihydro-1H-pyrrole,3-ethyl-1,5-dimethyl-2,3-dihydro-1H-pyrrole,3-ethyl-1,4-dimethyl-2,3-dihydro-1H-pyrrole,3-ethyl-1,2-dimethyl-2,3-dihydro-1H-pyrrole,2-ethyl-1,5-dimethyl-2,3-dihydro-1H-pyrrole,2-ethyl-1,4-dimethyl-2,3-dihydro-1H-pyrrole,2-ethyl-1,3-dimethyl-2,3-dihydro-1H-pyrrole,1-methyl-5-propyl-2,3-dihydro-1H-pyrrole,1-methyl-4-propyl-2,3-dihydro-1H-pyrrole,1-methyl-3-propyl-2,3-dihydro-1H-pyrrole,1-methyl-2-propyl-2,3-dihydro-1H-pyrrole,5-isopropyl-1-methyl-2,3-dihydro-1H-pyrrole,4-isopropyl-1-methyl-2,3-dihydro-1H-pyrrole,3-isopropyl-1-methyl-2,3-dihydro-1H-pyrrole,2-isopropyl-1-methyl-2,3-dihydro-1H-pyrrole, pyridine, 1-methylpyridine, 2-methyl pyridine, 3-methyl pyridine, 2,3-dimethyl pyridine,2,4-dimethylpyridine, 2,5-dimethylpyridine, 2,6-dimethylpyridine,3,4-dimethylpyridine, 3,5-dimethylpyridine, 2-ethyl pyridine, 3-ethylpyridine and 4-ethyl pyridine, a pyrimidine, 2-methylpyrimidine,4-methylpyrimidine, 5-methylpyrimidine, 2,4-dimethylpyrimidine,2,5-dimethylpyrimidine, 4,5-dimethylpyrimidine, 4,6-dimethylpyrimidine,2-ethylpyrimidine, 4-ethylpyrimidine, 5-ethylpyrimidine, isoxazole,3-methylisoxazole, 4-methylisoxazole, 5-methylisoxazole,3,4-dimethylisoxazole, 3,5-dimethylisoxazole, 4,5-dimethylisoxazole,3,4,5-trimethylisoxazole, 3-ethylisoxazole, 4-ethylisoxazole, 5-ethylisoxazole, 3-ethyl-4-methylisoxazole, 3-ethyl-5-methylisoxazole,4-ethyl-3-methylisoxazole, 4-ethyl-5-methylisoxazole,5-ethyl-3-methylisoxazole, 5-ethyl-4-methylisoxazole, 3-propylisoxazole,4-propylisoxazole, 5-propylisoxazole, 3-isopropylisoxazole, 4-isopropylisozazole, 5-isopropylisoxazole, 1-methyl imidazole,1,2-dimethyl-1H-imidazole, 1,4-dimethyl-1H-imidazole,1,5-dimethyl-1H-imidazole, 1,2,4-trimethyl-1H-imidazole,1,2,5-trimethyl-1H-imidazole, 1,4,5-trimethyl-1H-imidazole,2-ethyl-1-methyl-1H-imidazole, 4-ethyl-1-methyl-1H-imidazole,5-ethyl-1-methyl-1H-imidazole, 1-ethyl-1H-imidazole,1-ethyl-2-methyl-1H-imidazole, 1-ethyl-4-methyl-1H-imidazole,1-ethyl-5-methyl-1H-imidazole, 1-methyl-1H-pyrazole,1,3-dimethyl-1H-pyrazole, 1,4-dimethyl-1H-pyrazole,1,5-dimethyl-1H-pyrazole, 1,3,4-trimethyl-1H-pyrazole,1,3,5-trimethyl-1H-pyrazole, 1,4,5-trimethyl-1H-pyrazole.

Other suitable compounds for use herein are are similar to those listedabove in which one or more of the methyl substituents is replaced with adifferent alkyl group, for example an ethyl or propyl substituent.

Tertiary amine compounds including primary or secondary amine groups arewithin the scope of the invention provided these groups do not preventquaternisation of the tertiary amine species.

The tertiary amine compounds of formula R══NR¹ preferably do not includeany free primary or secondary amine groups. The tertiary amine compoundof formula R══NR¹ may contain more than one tertiary amine group.

Some preferred compounds of formula R══NR¹ include 1-methyl pyrrolidine,1-methylimidazole, 1,2-dimethyl-1H-imidazole, pyridine and mixtures andisomers thereof. 8-hydroxyquinoline could also be used.

Especially preferred tertiary amine compounds of formula R══NR¹ includemethyl pyrollidine and methyl imidazole.

Other suitable compounds would be known to the person skilled in theart.

In one embodiment the quaternising agent is (i) an ester of formulaR⁵COOR².

In such embodiments R² is a C₁ to C₇ alkyl group and R⁵ is the residueof a carboxylic acid selected from a substituted aromatic carboxylicacid, an a-hydroxycarboxylic acid and a polycarboxylic acid.

Preferred ester quaternising agents are compounds of formula (X):

in which R⁵ and R² are as previously defined herein. The compound offormula (X) is suitably an ester of a carboxylic acid capable ofreacting with a tertiary amine to form a quaternary ammonium salt.

Suitable quaternising agents include esters of carboxylic acids having apKa of 3.5 or less.

The compound of formula (X) is preferably an ester of a carboxylic acidselected from a substituted aromatic carboxylic acid, anα-hydroxycarboxylic acid and a polycarboxylic acid.

In some preferred embodiments the compound of formula (X) is an ester ofa substituted aromatic carboxylic acid and thus R⁵ is a substituted arylgroup.

Especially preferred compounds of formula (X) are lower alkyl esters ofsalicylic acid such as methyl salicylate, ethyl salicylate, n andi-propyl salicylate, and butyl salicylate, preferably methyl salicylate.

In some embodiments the compound of formula (X) is an ester of ana-hydroxycarboxylic acid. In such embodiments the compound has thestructure:

wherein R^(x) and R^(y) are the same or different and each is selectedfrom hydrogen, alkyl, alkenyl, or aryl. Compounds of this type suitablefor use herein are described in EP 1254889.

A preferred compound of this type is methyl 2-hydroxyisobutyrate.

In some embodiments the compound of formula (X) is an ester of apolycarboxylic acid. In this definition we mean to include dicarboxylicacids and carboxylic acids having more than 2 acidic moieties.

One especially preferred compound of formula (X) is dimethyl oxalate.

The ester quaternising agent may be selected from an ester of acarboxylic acid selected from one or more of oxalic acid, phthalic acid,tartaric acid, salicylic acid, maleic acid, malonic acid, citric acid,nitrobenzoic acid, aminobenzoic acid and 2,4,6-trihydroxybenzoic acid.

Preferred ester quaternising agents include dimethyl oxalate, methyl2-nitrobenzoate, dimethylphthalate, dimethyltartrate and methylsalicylate.

In some embodiments the quaternary ammonium salts are prepared byreacting a tertiary amine of formula R══NR¹ with (ii) a carbonate offormula R⁴OCOOR² and then with a carboxylic acid of formula R⁵COOH. R²is as defined above. R⁴ is preferably an optionally substituted alkylalkenyl or aryl group having up to 30 carbon atoms. Preferably R⁴ is anoptionally substituted alkyl group. Preferably R⁴ is an alkyl grouphaving up to 24 carbon atoms, preferably up to 20 carbon atoms, suitablyup to 16 carbon atoms, preferably up to 12 carbon atoms, suitably up to8, for example up to 6 or up to 4 carbon atoms.

Preferably R⁴ is an unsubstituted alkyl group. In one embodiment R⁴ maybe the same or different to R². Preferably R⁴ is the same as R².Preferred carbonates are diethyl carbonate and dimethyl carbonate.Dimethyl carbonate is especially preferred. Once the tertiary amine hasbeen reacted with a carbonate quaternising group the resulting salt isthen reacted with a carboxylic acid of formula R⁵COOH to provide acompound of the first aspect.

The carboxylic acid of formula R⁵COOH may be a very small simplemolecule. In some embodiments it may be a simple fatty acid compound.However it may also be a more complex molecule including additional acidfunctional groups.

Examples of suitable small simple acids include formic acid, aceticacid, propionic acid and butyric acid.

Examples of suitable fatty acids include caprylic acid, capris acid,lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid,behenic acid, lignoceric acid, cerotic acid, myristoleic acid,palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenicacid, linoleic acid, linoelaidic acid, arachidonic acid,eicosapentaenoic acid, erucic acid, undecylenic acid and docosahexenoicacid.

Suitable complex acids include optionally substituted phthalic acid andsuccinic acid derivatives.

In embodiments in which the acid includes more than one acid functionalgroup the further groups may be present as the free acid or the ester.Where there is more than one free acid group there is suitably anequivalent number of cations.

In some preferred embodiments the quaternising agent is (iii) thecombination of an epoxide and a carboxylic acid of formula R⁵COOH.

Suitably the quaternary ammonium salts of the present invention areprepared by the reaction of a tertiary amine of formula R══NR¹ with anepoxide and R² is the residue of the epoxide.

The present invention suitably provides a quaternary ammonium compoundwhich is the reaction product of:

-   -   (a) a cyclic tertiary amine having less than 19 carbon atoms;    -   (b) an epoxide having less than 8 carbon atoms; and    -   (c) a carboxylic acid of formula R⁵COOH; wherein R⁵ is hydrogen        or an optionally substituted hydrocarbyl group.

According to a second aspect of the present invention there is provideda method of preparing a quaternary ammonium salt, the method comprisingreacting (a) a cyclic tertiary amine having less than 19 carbon atomswith (b) an epoxide having less than 8 carbon atoms in the presence of(c) a carboxylic acid of formula R⁵COOH; wherein R⁵ is hydrogen or anoptionally substituted hydrocarbyl group.

Preferred features of the second aspect of the invention are as definedin relation to the first aspect. Further preferred features of theinvention will now be described which apply to the first and secondaspects.

Component (a) is a cyclic tertiary amine having less than 19 carbonatoms.

Suitably the cyclic tertiary amine (a) has the formula R══NR¹ wherein R¹is an optionally substituted alkyl, alkenyl or aryl group having lessthan 8 carbons and R together with N forms an aliphatic or aromaticheterocycle having less 12 carbon atoms. R¹ and the heterocycle formedby R and N are preferably as described in relation to the first aspect.

Especially preferred tertiary amine compounds for use as component (a)include methyl pyrollidine and methyl imidazole.

Any suitable epoxide compound having less than 8 carbon atoms may beused as component (b). Suitable epoxide compounds are those of formula:

wherein each of R⁶, R⁷, R⁸, R⁹ is independently selected from hydrogenor an optionally substituted alkyl, alkenyl or aryl group.

At least one of R⁶, R⁷, R⁸ and R⁹ is hydrogen. Preferably at least twoof R⁶, R⁷, R⁸ and R⁹ are hydrogen. Most preferably three of of R⁶, R⁷,R⁸ and R⁹ are hydrogen. of R⁶, R⁷, R⁸ and R⁹ may be all hydrogen.

In the structure above and the definitions which follow R⁶ and R⁷ areinterchangeable and thus when these groups are different eitherenantiomer or diastereomer may be used as component (b).

In the structure above and the definitions which follow R⁸ and R⁹ areinterchangeable and thus when these groups are different eitherenantiomer or diastereomer may be used as component (b).

Preferably R⁶ is hydrogen or an optionally substituted alkyl, alkenyl oraryl group. Most preferably R⁶ is hydrogen.

Preferably R⁷ is hydrogen or an optionally substituted alkyl, alkenyl oraryl group. Most preferably R⁷ is hydrogen.

Preferably R⁸ is hydrogen or an optionally substituted alkyl, alkenyl oraryl group. Most preferably R⁸ is hydrogen.

Preferably R⁹ is hydrogen or an optionally substituted alkyl, alkenyl oraryl group. Preferably R⁹ is an alkyl group having 1 to 5 carbon atoms.In some embodiments R⁹ may include an oxygen atom in the carbon chain,i.e. R⁹ may include an ether functional group.

Preferred epoxide compounds for use as component (b) include ethyleneoxide, propylene oxide, butylene oxide, pentylene oxide, hexylene oxideand heptylene oxide. These may be provided as appropriate in anyisomeric form or as a mixture of isomers. Also useful are glycidyl ethercompounds, for example isopropyl glycidyl ether.

In some especially preferred embodiments component (b) is selected from1,2-epoxy butane and isopropyl glycidyl ether.

Component (c) used to prepare the quaternary ammonium salts of thepresent invention is a carboxylic acid of formula R⁵COOH.

Component (c) includes a carboxylic acid functional group. it may be avery small simple molecule. In some embodiments component (c) may be asimple fatty acid compound. However component (c) may also be a morecomplex molecule including additional acid functional groups.

For the avoidance of doubt component (c) is an acid which activates thealkylating agent (b) and forms the anionic counterion of the quaternaryammonium salt.

Example of suitable small simple acids for use as component (c) includeformic acid, acetic acid, propionic acid and butyric acid.

Suitable fatty acids for use as component (c) include caprylic acid,capris acid, lauric acid, myristic acid, palmitic acid, stearic acid,arachidic acid, behenic acid, lignoceric acid, cerotic acid, myristoleicacid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid,vaccenic acid, linoleic acid, linoelaidic acid, arachidonic acid,eicosapentaenoic acid, erucic acid, undecylenic acid and docosahexenoicacid.

Suitable complex acids for use as component (c) may be an optionallysubstituted phthalic acid and succinic acid derivatives.

In embodiments in which component (c) includes more than one acidfunctional group the further groups may be present as the free acid orthe ester. Where there is more than one free acid group there issuitably an equivalent number of cations.

For example for in the case of diacid components (a), (b) and (c) arepreferably reacted in a molar ratio of 2±0.5: 2±0.5:1; preferably 2±0.2:2±0.2:1, more preferably 2±0.1: 2±0.1:1.

The quaternary ammonium compounds of the present invention have beenfound to be effective as deposit control additives for use in fuel orlubricating additives.

Thus the present invention provides the use of a quaternary ammoniumcompound of the first aspect as an additive for fuel or lubricating oilcompositions.

The present invention may provide the use of a quaternary ammoniumcompound of the first aspect as a deposit control additive for fuel orlubricating oil compositions.

The present invention may provide the use of a quaternary ammoniumcompound of the first aspect as a deposit control additive forlubricating oil compositions.

The present invention may provide the use of a quaternary ammoniumcompound of the first aspect as a deposit control additive for fuelcompositions.

The present invention may provide the use of a quaternary ammoniumcompound of the first aspect as a deposit control additive for gasolineor diesel fuel compositions.

The present invention may provide the use of a quaternary ammoniumcompound of the first aspect as a deposit control additive for gasolinefuel compositions.

The present invention may provide the use of a quaternary ammoniumcompound of the first aspect as a deposit control additive for dieselfuel compositions.

According to a third aspect of the present invention there is providedan additive composition comprising a quaternary ammonium salt of thefirst aspect and a diluent or carrier.

The additive composition of the third aspect may be an additivecomposition for lubricating oil.

The additive composition of the third aspect may be an additivecomposition for gasoline.

Preferably the additive composition of the third aspect is an additivecomposition for diesel fuel.

The quaternary ammonium compound is suitably present in the additivecomposition in an amount of from 1 to 99 wt %, for example from 1 to 75wt %.

The additive composition may comprise a mixture of two or morequaternary ammonium compounds of the present invention. In suchembodiments the above amounts suitably refer to the total amount of allsuch compounds present in the composition.

The additive composition may include one or more further additives.These may be selected from antioxidants, dispersants, detergents, metaldeactivating compounds, wax anti-settling agents, cold flow improvers,cetane improvers, dehazers, stabilisers, demulsifiers, antifoams,corrosion inhibitors, lubricity improvers, dyes, markers, combustionimprovers, metal deactivators, odour masks, drag reducers andconductivity improvers.

In some preferred embodiments the additive composition includes one ormore further nitrogen-containing detergents.

The present invention may provide a fuel or lubricating oil compositioncomprising a quaternary ammonium salt of the first aspect.

According to a fourth aspect of the present invention there is provideda lubricating composition comprising an oil of lubricating viscosity andas an additive a quaternary ammonium salt of the first aspect.

Preferred features of the quaternary ammonium compound are as defined inrelation to the first and second aspects.

The additive composition of the third aspect suitably upon dilutionprovides a lubricating composition of the fourth aspect.

According to a fifth aspect of the present invention there is provided afuel composition comprising as an additive a quaternary ammonium salt ofthe first aspect.

Preferred features of the quaternary ammonium compound are as defined inrelation to the first and second aspects.

The additive composition of the third aspect suitably upon dilutionprovides a fuel composition of the fifth aspect.

The present invention may further provide a method of preparing a fuelcomposition, the method comprising preparing a quaternary ammonium saltaccording to the method of the second aspect, and mixing the quaternaryammonium salt into the fuel.

Additives of the invention may be added to diesel fuel at any convenientplace in the supply chain. For examples, the additives may be added tofuel at the refinery, at a distribution terminal or after the fuel hasleft the distribution terminal. If the additive is added to the fuelafter it has left the distribution terminal, this is termed anaftermarket application. Aftermarket applications include suchcircumstances as adding the additive to the fuel in the delivery tanker,directly to a customer's bulk storage tank, or directly to the enduser's vehicle tank. Aftermarket applications may include supplying thefuel additive in small bottles suitable for direct addition to fuelstorage tanks or vehicle tanks.

The composition of the present invention may be a gasoline compositionor a diesel fuel composition. Preferably it is a diesel fuelcomposition.

By diesel fuel we include any fuel suitable for use in a diesel engineeither for road use or non-road use. This includes but is not limited tofuels described as diesel, marine diesel, heavy fuel oil, industrialfuel oil, etc.

The diesel fuel composition of the present invention may comprise apetroleum-based fuel oil, especially a middle distillate fuel oil. Suchdistillate fuel oils generally boil within the range of from 110° C. to500° C., e.g. 150° C. to 400° C. The diesel fuel may compriseatmospheric distillate or vacuum distillate, cracked gas oil, or a blendin any proportion of straight run and refinery streams such as thermallyand/or catalytically cracked and hydro-cracked distillates.

The diesel fuel composition of the present invention may comprisenon-renewable Fischer-Tropsch fuels such as those described as GTL(gas-to-liquid) fuels, CTL (coal-to-liquid) fuels and OTL (oilsands-to-liquid).

The diesel fuel composition of the present invention may comprise arenewable fuel such as a biofuel composition or biodiesel composition.

The diesel fuel composition may comprise 1st generation biodiesel. Firstgeneration biodiesel contains esters of, for example, vegetable oils,animal fats and used cooking fats. This form of biodiesel may beobtained by transesterification of oils, for example rapeseed oil,soybean oil, safflower oil, palm oil, corn oil, peanut oil, cotton seedoil, tallow, coconut oil, physic nut oil (Jatropha), sunflower seed oil,used cooking oils, hydrogenated vegetable oils or any mixture thereof,with an alcohol, usually a monoalcohol, usually in the presence of acatalyst.

The diesel fuel composition may comprise second generation biodiesel.Second generation biodiesel is derived from renewable resources such asvegetable oils and animal fats and processed, often in the refinery,often using hydroprocessing such as the H-Bio process developed byPetrobras. Second generation biodiesel may be similar in properties andquality to petroleum based fuel oil streams, for example renewablediesel produced from vegetable oils, animal fats etc. and marketed byConocoPhillips as Renewable Diesel and by Neste as NExBTL.

The diesel fuel composition of the present invention may comprise thirdgeneration biodiesel. Third generation biodiesel utilises gasificationand Fischer-Tropsch technology including those described as BTL(biomass-to-liquid) fuels. Third generation biodiesel does not differwidely from some second generation biodiesel, but aims to exploit thewhole plant (biomass) and thereby widens the feedstock base.

The diesel fuel composition may contain blends of any or all of theabove diesel fuel compositions.

In some embodiments the diesel fuel composition of the present inventionmay be a blended diesel fuel comprising bio-diesel. In such blends thebio-diesel may be present in an amount of, for example up to 0.5%, up to1%, up to 2%, up to 3%, up to 4%, up to 5%, up to 10%, up to 20%, up to30%, up to 40%, up to 50%, up to 60%, up to 70%, up to 80%, up to 90%,up to 95% or up to 99%.

In some embodiments the fuel composition may comprise neat biodiesel.

In some embodiments the fuel composition may comprise a neat GTL fuel.

In some embodiments the diesel fuel composition may comprise a secondaryfuel, for example ethanol. Preferably however the diesel fuelcomposition does not contain ethanol.

The diesel fuel composition of the present invention may contain arelatively high sulphur content, for example greater than 0.05% byweight, such as 0.1% or 0.2%.

However in preferred embodiments the diesel fuel has a sulphur contentof at most 0.05% by weight, more preferably of at most 0.035% by weight,especially of at most 0.015%. Fuels with even lower levels of sulphurare also suitable such as, fuels with less than 50 ppm sulphur byweight, preferably less than 20 ppm, for example 10 ppm or less.

Suitably the quaternary ammonium salt additive is present in the dieselfuel composition in an amount of at least 0.1 ppm, preferably at least 1ppm, more preferably at least 5 ppm, suitably at least 10 ppm, forexample at least 20 ppm or at least 25 ppm.

Suitably the quaternary ammonium salt additive is present in the dieselfuel composition in an amount of less than 10000ppm, preferably lessthan 1000 ppm, preferably less than 500 ppm, preferably less than 250ppm, suitably less than 200 ppm, for example less than 150 ppm or lessthan 100 ppm.

The diesel fuel composition of the fifth aspect of the present inventionmay comprise a mixture of two or more quaternary ammonium salts of thefirst aspect. In such embodiments the above amounts refer to the totalamounts of all such additives present in the composition.

The diesel fuel composition of the present invention may include one ormore further additives such as those which are commonly found in dieselfuels. These include, for example, antioxidants, dispersants,detergents, metal deactivating compounds, wax anti-settling agents, coldflow improvers, cetane improvers, dehazers, stabilisers, demulsifiers,antifoams, corrosion inhibitors, lubricity improvers, dyes, markers,combustion improvers, metal deactivators, odour masks, drag reducers andconductivity improvers. Examples of suitable amounts of each of thesetypes of additives will be known to the person skilled in the art.

In some preferred embodiments the diesel fuel composition of the presentinvention comprises one or more further detergents. Nitrogen-containingdetergents are preferred.

The one or more further detergents may be selected from:

-   -   (i) an additional quaternary ammonium salt additive which is not        a quaternary ammonium compound of the first aspect;    -   (ii) the product of a Mannich reaction between an aldehyde, an        amine and an optionally substituted phenol;    -   (iii) the reaction product of a carboxylic acid-derived        acylating agent and an amine;    -   (iv) the reaction product of a carboxylic acid-derived acylating        agent and hydrazine;    -   (v) a salt formed by the reaction of a carboxylic acid with        di-n-butylamine or tri-n-butylamine;    -   (vi) the reaction product of a hydrocarbyl-substituted        dicarboxylic acid or anhydride and an amine compound or salt        which product comprises at least one amino triazole group; and    -   (vii) a substituted polyaromatic detergent additive.

In some embodiments the diesel fuel composition comprises an additionalquaternary ammonium salt additive which is not a quaternary ammoniumcompound of the first aspect.

The additional quaternary ammonium salt additive is suitably thereaction product of a nitrogen-containing species having at least onetertiary amine group and a quaternising agent.

The nitrogen containing species may be selected from:

-   -   (x) the reaction product of a hydrocarbyl-substituted acylating        agent and a compound comprising at least one tertiary amine        group and a primary amine, secondary amine or alcohol group;    -   (y) a Mannich reaction product comprising a tertiary amine        group; and    -   (z) a polyalkylene substituted amine having at least one        tertiary amine group.

Examples of quaternary ammonium salt and methods for preparing the sameare described in the following patents, which are hereby incorporated byreference, US2008/0307698, US2008/0052985, US2008/0113890 andUS2013/031827.

Component (x) may be regarded as the reaction product of ahydrocarbyl-substituted acylating agent and a compound having an oxygenor nitrogen atom capable of condensing with said acylating agent andfurther having a tertiary amino group. Preferred features of thesecompounds are as described above in relation to tertiary amine component(a) used to prepare the quaternary ammonium salt additives of thepresent invention.

The preparation of some suitable quaternary ammonium salt additives inwhich the nitrogen-containing species includes component (x) isdescribed in WO 2006/135881 and WO2011/095819.

Component (y) is a Mannich reaction product having a tertiary amine. Thepreparation of quaternary ammonium salts formed from nitrogen-containingspecies including component (y) is described in US 2008/0052985.Preferred features of these compounds are as described above in relationto tertiary amine component (a) used to prepare the quaternary ammoniumsalt additives of the present invention.

The preparation of quaternary ammonium salt additives in which thenitrogen-containing species includes component (z) is described forexample in US 2008/0113890. Preferred features of these compounds are asdescribed above in relation to tertiary amine component (a) used toprepare the quaternary ammonium salt additives of the present invention.

To form the additional quaternary ammonium salt additives (I), thenitrogen containing species having a tertiary amine group is reactedwith a quaternizing agent.

The quaternising agent may suitably be selected from esters andnon-esters.

In some preferred embodiments, quaternising agents used to form thequaternary ammonium salt additives of the present invention are esters.

Preferred ester quaternising agents are compounds of formula (III):

in which R is an optionally substituted alkyl, alkenyl, aryl oralkylaryl group and R¹ is a C₁ to C₂₂ alkyl, aryl or alkylaryl group.The compound of formula (III) is suitably an ester of a carboxylic acidcapable of reacting with a tertiary amine to form a quaternary ammoniumsalt.

Suitable quaternising agents include esters of carboxylic acids having apKa of 3.5 or less.

The compound of formula (III) is preferably an ester of a carboxylicacid selected from a substituted aromatic carboxylic acid, ana-hydroxycarboxylic acid and a polycarboxylic acid.

In some preferred embodiments the compound of formula (III) is an esterof a substituted aromatic carboxylic acid and thus R is a subsitutedaryl group.

Especially preferred compounds of formula (III) are lower alkyl estersof salicylic acid such as methyl salicylate, ethyl salicylate, n andi-propyl salicylate, and butyl salicylate, preferably methyl salicylate.

In some embodiments the compound of formula (III) is an ester of ana-hydroxycarboxylic acid. In such embodiments the compound has thestructure:

wherein R⁷ and R⁸ are the same or different and each is selected fromhydrogen, alkyl, alkenyl, aralkyl or aryl. Compounds of this typesuitable for use herein are described in EP 1254889.

A preferred compound of this type is methyl 2-hydroxyisobutyrate.

In some embodiments the compound of formula (III) is an ester of apolycarboxylic acid. In this definition we mean to include dicarboxylicacids and carboxylic acids having more than 2 acidic moieties.

One especially preferred compound of formula (III) is dimethyl oxalate.

The ester quaternising agent may be selected from an ester of acarboxylic acid selected from one or more of oxalic acid, phthalic acid,tartaric acid, salicylic acid, maleic acid, malonic acid, citric acid,nitrobenzoic acid, aminobenzoic acid and 2, 4, 6-trihydroxybenzoic acid.

Preferred ester quaternising agents include dimethyl oxalate, methyl2-nitrobenzoate, dimethyl phthalate, dimethyl tartrate and methylsalicylate.

Suitable non-ester quaternising agents include dialkyl sulfates, benzylhalides, hydrocarbyl substituted carbonates, hydrocarbyl susbsitutedepoxides in combination with an acid, alkyl halides, alkyl sulfonates,sultones, hydrocarbyl substituted phosphates, hydrocarbyl substitutedborates, alkyl nitrites, alkyl nitrates, hydroxides, N-oxides ormixtures thereof.

In some embodiments the quaternary ammonium salt may be prepared from,for example, an alkyl or benzyl halide (especially a chloride) and thensubjected to an ion exchange reaction to provide a different anion aspart of the quaternary ammonium salt. Such a method may be suitable toprepare quaternary ammonium hydroxides, alkoxides, nitrites or nitrates.

Preferred non-ester quaternising agents include dialkyl sulfates, benzylhalides, hydrocarbyl substituted carbonates, hydrocarbyl substitutedepoxides in combination with an acid, alkyl halides, alkyl sulfonates,sultones, hydrocarbyl substituted phosphates, hydrocarbyl substitutedborates, N-oxides or mixtures thereof.

Suitable dialkyl sulfates for use herein as quaternising agents includethose including alkyl groups having 1 to 10 carbons atoms in the alkylchain. A preferred compound is dimethyl sulfate.

Suitable benzyl halides include chlorides, bromides and iodides. Apreferred compound is benzyl bromide.

Suitable hydrocarbyl substituted carbonates may include two hydrocarbylgroups, which may be the same or different. Preferred compounds of thistype include diethyl carbonate and dimethyl carbonate.

Suitable hydrocarbyl susbsituted epoxides have the formula:

wherein each of R¹, R², R³ and R⁴ is independently hydrogen or ahydrocarbyl group having 1 to 50 carbon atoms. Examples of suitableepoxides include ethylene oxide, propylene oxide, butylene oxide,styrene oxide and stillbene oxide. The hydrocarbyl epoxides are used asquaternising agents in combination with an acid. In such embodiments theacid is not an acid of the type defined in relation to component (c)used to prepare the quaternary ammonium salts of the present invention.

In embodiments in which the hydrocarbyl substituted acylating agent hasmore than one acyl group no separate acid needs to be added. However inother embodiments an acid such as acetic acid may be used.

Especially preferred epoxide quaternising agents are propylene oxide andstyrene oxide.

Suitable sultones include propane sultone and butane sultone.

Suitable hydrocarbyl substituted phosphates include dialkyl phosphates,trialkyl phosphates and O,O-dialkyl dithiophosphates.

Suitable hydrocarbyl substituted borate groups include alkyl borateshaving 1 to 12 carbon atoms.

Preferred alkyl nitrites and alkyl nitrates have 1 to 12 carbon atoms.

Preferably the non-ester quaternising agent is selected from dialkylsulfates, benzyl halides, hydrocarbyl substituted carbonates,hydrocarbyl susbsituted epoxides in combination with an acid, andmixtures thereof.

Especially preferred non-ester quaternising agents for use herein arehydrocarbyl substituted epoxides in combination with an acid. These mayinclude embodiments in which a separate acid is provided or embodimentsin which the acid is provided by the tertiary amine compound that isbeing quaternised. Preferably the acid is provided by the tertiary aminemolecule that is being quaternised.

Preferred quaternising agents for use herein include dimethyl oxalate,methyl 2-nitrobenzoate, methyl salicylate and styrene oxide or propyleneoxide optionally in combination with an additional acid.

An especially preferred additonal quaternary ammonium salt for useherein is formed by reacting methyl salicylate or dimethyl oxalate withthe reaction product of a polyisobutylene-substituted succinic anhydridehaving a PIB molecular weight of 700 to 1300 anddimethylaminopropylamine.

Other suitable additional quaternary ammonium salts include quaternisedterpolymers, for example as described in US2011/0258917; quaternisedcopolymers, for example as described in US2011/0315107; and theacid-free quaternised nitrogen compounds disclosed in US2012/0010112.

Further suitable additional quaternary ammonium compounds for use in thepresent invention include the quaternary ammonium compounds described inthe applicants copending application WO2013/017889.

In some embodiments the diesel fuel composition comprises the product ofa Mannich reaction between an aldehyde, an amine and an optionallysubstituted phenol. This Mannich reaction product is suitably not aquaternary ammonium salt.

Preferably the aldehyde component used to prepare the Mannich additiveis an aliphatic aldehyde. Preferably the aldehyde has 1 to 10 carbonatoms. Most preferably the aldehyde is formaldehyde.

The amine used to prepare the Mannich additive is preferably apolyamine. This may be selected from any compound including two or moreamine groups. Preferably the polyamine is a polyalkylene polyamine,preferably a polyethylene polyamine. Most preferably the polyaminecomprises tetraethylenepentamine or ethylenediamine.

The optionally substituted phenol component used to prepare the Mannichadditive may be substituted with 0 to 4 groups on the aromatic ring (inaddition to the phenol OH). For example it may be ahydrocarbyl-substituted cresol. Most preferably the phenol component isa mono-substituted phenol. Preferably it is a hydrocarbyl substitutedphenol. Preferred hydrocarbyl substituents are alkyl substituents having4 to 28 carbon atoms, especially 10 to 14 carbon atoms. Other preferredhydrocarbyl substituents are polyalkenyl substituents suchpolyisobutenyl substituents having an average molecular weight of from400 to 2500, for example from 500 to 1500.

In some embodiments the diesel fuel composition comprises the reactionproduct of a carboxylic acid-derived acylating agent and an amine.

These may also be referred to herein in general as acylatednitrogen-containing compounds.

Suitable acylated nitrogen-containing compounds may be made by reactinga carboxylic acid acylating agent with an amine and are known to thoseskilled in the art.

Preferred acylated nitrogen-containing compounds are hydrocarbylsubstituted. The hydrocarbyl substituent may be in either the carboxylicacid acylating agent derived portion of the molecule or in the aminederived portion of the molecule, or both. Preferably, however, it is inthe acylating agent portion. A preferred class of acylatednitrogen-containing compounds suitable for use in the present inventionare those formed by the reaction of an acylating agent having ahydrocarbyl substituent of at least 8 carbon atoms and a compoundcomprising at least one primary or secondary amine group.

The acylating agent may be a mono- or polycarboxylic acid (or reactiveequivalent thereof) for example a substituted succinic, phthalic orpropionic acid or anhydride.

The term “hydrocarbyl” is previously defined herein. The hydrocarbylsubstituent in such acylating agents preferably comprises at least 10,more preferably at least 12, for example at least 30 or at least 40carbon atoms. It may comprise up to about 200 carbon atoms. Preferablythe hydrocarbyl substituent of the acylating agent has a number averagemolecular weight (Mn) of between 170 to 2800, for example from 250 to1500, preferably from 500 to 1500 and more preferably 500 to 1100. An Mnof 700 to 1300 is especially preferred. In a particularly preferredembodiment, the hydrocarbyl substituent has a number average molecularweight of 700-1000, preferably 700-850 for example 750.

Preferred hydrocarbyl-based substituents are polyisobutenes. Suchcompounds are known to the person skilled in the art.

Preferred hydrocarbyl substituted acylating agents are polyisobutenylsuccinic anhydrides. These compounds are commonly referred to as“PIBSAs” and are known to the person skilled in the art.

Conventional polyisobutenes and so-called “highly-reactive”polyisobutenes are suitable for use in the invention.

Especially preferred PIBSAs are those having a PIB molecular weight (Mn)of from 300 to 2800, preferably from 450 to 2300, more preferably from500 to 1300.

To prepare these additives the carboxylic acid-derived acylating agentis reacted with an amine. Suitably it is reacted with a primary orsecondary amine. Examples of suitable amines are known to the personskilled in the art and include polyalkylene polyamines,heterocyclic-substituted polyamines and aromatic polyamines.

Preferred amines are polyethylene polyamines including ethylenediamine,diethylenetriamine, triethylenetetramine, tetraethylenepentamine,pentaethylenehexamine, hexaethylene-heptamine, and mixtures and isomersthereof.

In preferred embodiments the reaction product of the carboxylic acidderived acylating agent and an amine includes at least one primary orsecondary amine group.

A preferred acylated nitrogen-containing compound for use herein isprepared by reacting a poly(isobutene)-substituted succinic acid-derivedacylating agent (e.g., anhydride, acid, ester, etc.) wherein thepoly(isobutene) substituent has a number average molecular weight (Mn)of between 170 to 2800 with a mixture of ethylene polyamines having 2 toabout 9 amino nitrogen atoms, preferably about 2 to about 8 nitrogenatoms, per ethylene polyamine and about 1 to about 8 ethylene groups.These acylated nitrogen compounds are suitably formed by the reaction ofa molar ratio of acylating agent:amino compound of from 10:1 to 1:10,preferably from 5:1 to 1:5, more preferably from 2:1 to 1:2 and mostpreferably from 2:1 to 1:1. In especially preferred embodiments, theacylated nitrogen compounds are formed by the reaction of acylatingagent to amino compound in a molar ratio of from 1.8:1 to 1:1.2,preferably from 1.6:1 to 1:1.2, more preferably from 1.4:1 to 1:1.1 andmost preferably from 1.2:1 to 1:1. Acylated amino compounds of this typeand their preparation are well known to those skilled in the art and aredescribed in for example EP0565285 and U.S. Pat. No. 5,925,151.

In some preferred embodiments the composition comprises a detergent ofthe type formed by the reaction of a polyisobutene-substituted succinicacid-derived acylating agent and a polyethylene polyamine. Suitablecompounds are, for example, described in W02009/040583.

In some embodiments the diesel fuel composition comprises the reactionproduct of a carboxylic acid-derived acylating agent and hydrazine.

Suitably the additive comprises the reaction product between ahydrocarbyl-substituted succinic acid or anhydride and hydrazine.

Preferably, the hydrocarbyl group of the hydrocarbyl-substitutedsuccinic acid or anhydride comprises a C₈-C₃₆ group, preferably a C₈-C₁₈group. Alternatively, the hydrocarbyl group may be a polyisobutylenegroup with a number average molecular weight of between 200 and 2500,preferably between 800 and 1200.

Hydrazine has the formula NH₂-NH_(2.) Hydrazine may be hydrated ornon-hydrated. Hydrazine monohydrate is preferred.

The reaction between the hydrocarbyl-substituted succinic acid oranhydride and hydrazine produces a variety of products, such as isdisclosed in US 2008/0060259.

In some embodiments the diesel fuel composition comprises a salt formedby the reaction of a carboxylic acid with di-n-butylamine ortri-n-butylamine. Exemplary compounds of this type are described in US2008/0060608.

Such additives may suitably be the di-n-butylamine or tri-n-butylaminesalt of a fatty acid of the formula [R′(COOH)_(x)]_(y′), where each R′is a independently a hydrocarbon group of between 2 and 45 carbon atoms,and x is an integer between 1 and 4.

In a preferred embodiment, the carboxylic acid comprises tall oil fattyacid (TOFA).

Further preferred features of additives of this type are described inEP1900795.

In some embodiments the diesel fuel composition comprises the reactionproduct of a hydrocarbyl-substituted dicarboxylic acid or anhydride andan amine compound or salt which product comprises at least one aminotriazole group.

Additives of this type are suitably the reaction product of ahydrocarbyl substituted dicarboxylic acid or anhydride and an aminecompound having the formula:

wherein R is selected from the group consisting of a hydrogen and ahydrocarbyl group containing from about 1 to about 15 carbon atoms, andR¹ is selected from the group consisting of hydrogen and a hydrocarbylgroup containing from about 1 to about 20 carbon atoms.

The additive suitably comprises the reaction product of an aminecompound having the formula:

and a hydrocarbyl carbonyl compound of the formula:

wherein R² is a hydrocarbyl group having a number average molecularweight ranging from about 100 to about 5000, preferably from 200 to3000.

Without being bound by theory, it is believed that the reaction productof the amine and hydrocarbyl carbonyl compound is an aminotriazole, suchas a bis-aminotriazole compound of the formula:

including tautomers having a number average molecular weight rangingfrom about 200 to about 3000 containing from about 40 to about 80 carbonatoms. The five-membered ring of the triazole is considered to bearomatic.

Further preferred features of additive compounds of this type are asdefined in US2009/0282731.

In some embodiments the diesel fuel composition comprises a substitutedpolyaromatic detergent additive.

One preferred compound of this type is the reaction product of anethoxylated naphthol and paraformaldehyde which is then reacted with ahydrocarbyl substituted acylating agent.

Further preferred features of these detergents are described inEP1884556.

In some embodiments the fuel composition may be a gasoline fuelcomposition.

Suitably the quaternary ammonium salt additive is present in thegasoline fuel composition in an amount of at least 0.1ppm, preferably atleast 1 ppm, more preferably at least 5 ppm, suitably at least 10 ppm,for example at least 20 ppm or at least 25 ppm.

Suitably the quaternary ammonium salt additive is present in thegasoline fuel composition in an amount of less than 10000ppm, preferablyless than 1000 ppm, preferably less than 500 ppm, preferably less than250 ppm, suitably less than 200 ppm, for example less than 150 ppm, orless than 100 ppm.

The gasoline fuel composition of the fifth aspect of the presentinvention may comprise a mixture of two or more quaternary ammoniumsalts of the first aspect. In such embodiments the above amounts referto the total amounts of all such additives present in the composition.

In such embodiments the composition may comprise one or more gasolinedetergents selected from:

-   -   (p) hydrocarbyl—substituted polyoxyalkylene amines or        polyetheramines;    -   (q) acylated nitrogen compounds which are the reaction product        of a carboxylic acid-derived acylating agent and an amine;    -   (r) hydrocarbyl-substituted amines wherein the hydrocarbyl        substituent is substantially aliphatic and contains at least 8        carbon atoms;    -   (s) Mannich base additives comprising nitrogen-containing        condensates of a phenol, aldehyde and primary or secondary        amine;    -   (t) aromatic esters of a polyalkylphenoxyalkanol;    -   (u) an additional quaternary ammonium salt additive which is not        a quaternary ammonium compound of the first aspect; and    -   (v) tertiary hydrocarbyl amines having a maximum of 30 carbon        atoms.

Suitable hydrocarbyl-substituted polyoxyalkylene amines orpolyetheramines (p) are described in U.S. Pat. Nos. 6,217,624 and4,288,612. Other suitable polyetheramines are those taught in U.S. Pat.Nos. 5,089,029 and 5,112,364.

The gasoline composition of the present invention may comprise as anadditive acylated nitrogen compounds (q) which are the reaction productof a carboxylic acid-derived acylating agent and an amine. Suchcompounds are preferably as previously defined herein in relation tocomponent (iii) of the additives which may be added to the diesel fuelcompositions of the invention.

Hydrocarbyl-substituted amines (r) suitable for use in the gasoline fuelcompositions of the present invention are well known to those skilled inthe art and are described in a number of patents. Among these are U.S.Pat. Nos. 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,755,433 and3,822,209. These patents describe suitable hydrocarbyl amines for use inthe present invention including their method of preparation.

The Mannich additives (s) comprise nitrogen-containing condensates of aphenol, aldehyde and primary or secondary amine, and are suitably asdefined in relation to component (ii) of the additives suitable for usein diesel fuel compositions.

The gasoline compositions of the present invention may further compriseas additives (t) aromatic esters of a polyalkylphenoxyalkanol.

The aromatic ester component which may be employed additive compositionis an aromatic ester of a polyalkylphenoxyalkanol and has the followinggeneral formula:

or a fuel-soluble salt(s) thereof wherein R is hydroxy, nitro or—(CH2)x-NR₅R₆, wherein R₅ and R₆ are independently hydrogen or loweralkyl having 1 to 6 carbon atoms and x is 0 or 1; R₁ is hydrogen,hydroxy, nitro or —NR₇R₈ wherein R₇ and R₈ are independently hydrogen orlower alkyl having 1 to 6 carbon atoms;

R₂ and R₃ are independently hydrogen or lower alkyl having 1 to 6 carbonatoms; and

R₄ is a polyalkyl group having an average molecular weight in the rangeof about 450 to 5,000.

Preferred features of these aromatic ester compounds are as described inWO2011141731.

The additional quaternary ammonium salt additives (u) are suitably asdefined in relation to component (i) of the additives suitable for usein diesel fuel compositions.

Tertiary hydrocarbyl amines (v) suitable for use in the gasoline fuelcompositions of the present invention are tertiary amines of the formulaR¹R²R³N wherein R¹, R²and R³ are the same or different C₁-C₂₀hydrocarbyl residues and the total number of carbon atoms is no morethan 30. Suitable examples are N,N dimethyl n dodecylamine,3-(N,N-dimethylamino) propanol and N,N-di(2-hydroxyethyl)-oleylamine.Preferred features of these tertiary hydrocarbyl amines are as describedin US2014/0123547.

The gasoline composition may further comprise a carrier oil.

The carrier oil may have any suitable molecular weight. A preferredmolecular weight is in the range 500 to 5000.

In one embodiment the carrier oil may comprise an oil of lubricatingviscosity, including natural or synthetic oils of lubricating viscosity,oil derived from hydrocracking, hydrogenation, hydrofinishing,unrefined, refined and re-refined oils, or mixtures thereof.

Natural oils include animal oils, vegetable oils, mineral oils ormixtures thereof. Synthetic oils may include hydrocarbon oils such asthose produced by Fischer-Tropsch reactions and typically may behydroisomerised Fischer-Tropsch hydrocarbons or waxes.

In another embodiment the carrier oil may comprise a polyether carrieroil. In a preferred embodiment the polyether carrier oil is a monoend-capped polyalkylene glycol, especially a mono end-cappedpolypropylene glycol. Carrier oils of this type will be known to theperson skilled in the art.

The gasoline fuel compositions of the invention may contain one or morefurther additives conventionally added to gasoline, for example otherdetergents, dispersants, anti-oxidants, anti-icing agents, metaldeactivators, lubricity additives, friction modifiers, dehazers,corrosion inhibitors, dyes, markers, octane improvers, anti-valve-seatrecession additives, stabilisers, demulsifiers, antifoams, odour masks,conductivity improvers and combustion improvers.

The quaternary ammonium salts of the present invention are useful asdeposit control additives for fuel and lubricating oil compositions. Theinclusion of these additives in fuel compositions has been found toreduce deposits within engines in which the fuel is combusted. This maybe achieved by preventing or reducing the formation of deposits, i.e.keeping the engine clean, or may be by the removal of existing deposits,i.e. cleaning up a fouled engine.

The quaternary ammonium compounds of the present invention have beenfound to be particularly effective in diesel engines, especially inmodern diesel engines having a high pressure fuel system.

Due to consumer demand and legislation, diesel engines have in recentyears become much more energy efficient, show improved performance andhave reduced emissions.

These improvements in performance and emissions have been brought aboutby improvements in the combustion process. To achieve the fuelatomisation necessary for this improved combustion, fuel injectionequipment has been developed which uses higher injection pressures andreduced fuel injector nozzle hole diameters. The fuel pressure at theinjection nozzle is now commonly in excess of 1500 bar (1.5×10⁸ Pa). Toachieve these pressures the work that must be done on the fuel alsoincreases the temperature of the fuel. These high pressures andtemperatures can cause degradation of the fuel. Furthermore, the timing,quantity and control of fuel injection has become increasingly precise.This precise fuel metering must be maintained to achieve optimalperformance.

Diesel engines having high pressure fuel systems can include but are notlimited to heavy duty diesel engines and smaller passenger car typediesel engines. Heavy duty diesel engines can include very powerfulengines such as the MTU series 4000 diesel having 20 cylinder variantsdesigned primarily for ships and power generation with power output upto 4300 kW or engines such as the Renault dXi 7 having 6 cylinders and apower output around 240kW. A typical passenger car diesel engine is thePeugeot DW10 having 4 cylinders and power output of 100 kW or lessdepending on the variant.

In preferred diesel engines relating to this invention, a common featureis a high pressure fuel system. Typically pressures in excess of 1350bar (1.35×10⁸ Pa) are used but often pressures of up to 2000 bar (2×10⁸Pa) or more may exist.

Two non-limiting examples of such high pressure fuel systems are: thecommon rail injection system, in which the fuel is compressed utilizinga high-pressure pump that supplies it to the fuel injection valvesthrough a common rail; and the unit injection system which integratesthe high-pressure pump and fuel injection valve in one assembly,achieving the highest possible injection pressures exceeding 2000 bar(2×10⁸ Pa). In both systems, in pressurising the fuel, the fuel getshot, often to temperatures around 100° C., or above.

In common rail systems, the fuel is stored at high pressure in thecentral accumulator rail or separate accumulators prior to beingdelivered to the injectors. Often, some of the heated fuel is returnedto the low pressure side of the fuel system or returned to the fueltank. In unit injection systems the fuel is compressed within theinjector in order to generate the high injection pressures. This in turnincreases the temperature of the fuel.

In both systems, fuel is present in the injector body prior to injectionwhere it is heated further due to heat from the combustion chamber. Thetemperature of the fuel at the tip of the injector can be as high as250-350° C.

Thus the fuel is stressed at pressures from 1350 bar (1.35×10⁸ Pa) toover 2000 bar (2×10⁸ Pa)and temperatures from around 100° C. to 350° C.prior to injection, sometimes being recirculated back within the fuelsystem thus increasing the time for which the fuel experiences theseconditions.

A common problem with diesel engines is fouling of the injector,particularly the injector body, and the injector nozzle. Fouling mayalso occur in the fuel filter. Injector nozzle fouling occurs when thenozzle becomes blocked with deposits from the diesel fuel. Fouling offuel filters may be related to the recirculation of fuel back to thefuel tank. Deposits increase with degradation of the fuel. Deposits maytake the form of carbonaceous coke-like residues, lacquers or sticky orgum-like residues. Diesel fuels become more and more unstable the morethey are heated, particularly if heated under pressure. Thus dieselengines having high pressure fuel systems may cause increased fueldegradation. In recent years the need to reduce emissions has led to thecontinual redesign of injection systems to help meet lower targets. Thishas led to increasingly complex injectors and lower tolerance todeposits.

The problem of injector fouling may occur when using any type of dieselfuels. However, some fuels may be particularly prone to cause fouling orfouling may occur more quickly when these fuels are used. For example,fuels containing biodiesel and those containing metallic species maylead to increased deposits.

When injectors become blocked or partially blocked, the delivery of fuelis less efficient and there is poor mixing of the fuel with the air.Over time this leads to a loss in power of the engine, increased exhaustemissions and poor fuel economy.

Deposits are known to occur in the spray channels of the injector,leading to reduced flow and power loss. As the size of the injectornozzle hole is reduced, the relative impact of deposit build up becomesmore significant. Deposits are also known to occur at the injector tip.Here, they affect the fuel spray pattern and cause less effectivecombustion and associated higher emissions and increased fuelconsumption.

In addition to these “external” injector deposits in the nozzle hole andat the injector tip which lead to reduced flow and power loss, depositsmay occur within the injector body causing further problems. Thesedeposits may be referred to as internal diesel injector deposits (orIDIDs). IDIDs occur inside the injector on the critical moving parts.They can hinder the movement of these parts affecting the timing andquantity of fuel injection. Since modern diesel engines operate undervery precise conditions these deposits can have a significant impact onperformance.

IDIDs cause a number of problems, including power loss and reduced fueleconomy due to less than optimal fuel metering and combustion. Initiallythe user may experience cold start problems and/or rough engine running.These deposits can lead to more serious injector sticking. This occurswhen the deposits stop parts of the injector from moving and thus theinjector stops working. When several or all of the injectors stick theengine may fail completely.

It is known to add nitrogen-containing detergents to diesel fuel toreduce coking. Typical nitrogen-containing detergents include thoseformed by the reaction of a polyisobutylene-substituted succinic acidderivative with a polyalkylene polyamine. However, newer enginesincluding finer injector nozzles are more sensitive and current dieselfuels may not be suitable for use with the new engines incorporatingthese smaller nozzle holes.

As mentioned above, the problem of injector fouling may be more likelyto occur when using fuel compositions comprising metal species. Variousmetal species may be present in fuel compositions. This may be due tocontamination of the fuel during manufacture, storage, transport or useor due to contamination of fuel additives. Metal species may also beadded to fuels deliberately. For example transition metals are sometimesadded as fuel borne catalysts, for example to improve the performance ofdiesel particulate filters.

The present inventors believe that problems of injector sticking occurwhen metal or ammonium species, particularly sodium species, react withcarboxylic acid species in the fuel.

Sodium contamination of diesel fuel and the resultant formation ofcarboxylate salts is believed to be a major cause of injector sticking.

In preferred embodiments the diesel fuel compositions used in thepresent invention comprise sodium and/or calcium. Preferably theycomprise sodium. The sodium and/or calcium is typically present in atotal amount of from 0.01 to 50 ppm, preferably from 0.05 to 5 ppmpreferably 0.1 to 2ppm such as 0.1 to 1 ppm.

Other metal-containing species may also be present as a contaminant, forexample through the corrosion of metal and metal oxide surfaces byacidic species present in the fuel or from lubricating oil. In use,fuels such as diesel fuels routinely come into contact with metalsurfaces for example, in vehicle fuelling systems, fuel tanks, fueltransportation means etc. Typically, metal-containing contamination maycomprise transition metals such as zinc, iron and copper; group I orgroup II metals and other metals such as lead.

The presence of metal containing species may give rise to fuel filterdeposits and/or external injector deposits including injector tipdeposits and/or nozzle deposits.

In addition to metal-containing contamination which may be present indiesel fuels there are circumstances where metal-containing species maydeliberately be added to the fuel. For example, as is known in the art,metal-containing fuel-borne catalyst species may be added to aid withthe regeneration of particulate traps. The presence of such catalystsmay also give rise to injector deposits when the fuels are used indiesel engines having high pressure fuel systems.

Metal-containing contamination, depending on its source, may be in theform of insoluble particulates or soluble compounds or complexes.Metal-containing fuel-borne catalysts are often soluble compounds orcomplexes or colloidal species.

In some embodiments, the diesel fuel may comprise metal-containingspecies comprising a fuel-borne catalyst. Preferably, the fuel bornecatalyst comprises one or more metals selected from iron, cerium,platinum, manganese, Group I and Group II metals e.g., calcium andstrontium. Most preferably the fuel borne catalyst comprises a metalselected from iron and cerium.

In some embodiments, the diesel fuel may comprise metal-containingspecies comprising zinc. Zinc may be present in an amount of from 0.01to 50 ppm, preferably from 0.05 to 5 ppm, more preferably 0.1 to 1.5ppm.

Typically, the total amount of all metal-containing species in thediesel fuel, expressed in terms of the total weight of metal in thespecies, is between 0.1 and 50 ppm by weight, for example between 0.1and 20 ppm, preferably between 0.1 and 10 ppm by weight, based on theweight of the diesel fuel.

It is advantageous to provide a diesel fuel composition which preventsor reduces the occurrence of deposits in a diesel engine. Such depositsmay include “external” injector deposits such as deposits in and aroundthe nozzle hole and at the injector tip and “internal” injector depositsor IDIDs. Such fuel compositions may be considered to perform a “keepclean” function i.e. they prevent or inhibit fouling. It is also bedesirable to provide a diesel fuel composition which would help clean updeposits of these types. Such a fuel composition which when combusted ina diesel engine removes deposits therefrom thus effecting the “clean-up”of an already fouled engine.

As with “keep clean” properties, “clean-up” of a fouled engine mayprovide significant advantages. For example, superior clean up may leadto an increase in power and/or an increase in fuel economy. In additionremoval of deposits from an engine, in particular from injectors maylead to an increase in interval time before injector maintenance orreplacement is necessary thus reducing maintenance costs.

Although for the reasons mentioned above deposits on injectors is aparticular problem found in modern diesel engines with high pressurefuels systems, it is desirable to provide a diesel fuel compositionwhich also provides effective detergency in older traditional dieselengines such that a single fuel supplied at the pumps can be used inengines of all types.

It is also desirable that fuel compositions reduce the fouling ofvehicle fuel filters. It is useful to provide compositions that preventor inhibit the occurrence of fuel filter deposits i.e, provide a “keepclean” function. It is useful to provide compositions that removeexisting deposits from fuel filter deposits i.e. provide a “clean up”function. Compositions able to provide both of these functions areespecially useful.

According to a sixth aspect of the present invention there is provided amethod of improving the performance of an engine, the method comprisingcombusting in said engine a fuel composition comprising as an additive aquaternary ammonium salt of formula:

wherein each of R¹ and R² is independently selected from an optionallysubstituted alkyl, alkenyl or aryl group having less than 8 carbonatoms, R together with N forms an aliphatic or aromatic group havingless than 12 carbon atoms and R⁵ is hydrogen or an optionallysubstituted hydrocarbyl group.

Preferred features of the sixth aspect of the present invention are asdefined in relation to the first, second, third and fifth aspects.

In the method of the fifth aspect the engine may be a gasoline engineand the fuel composition may be a gasoline fuel.

Preferably in the method of the fourth aspect the engine is a dieselengine and the fuel composition is a diesel fuel composition.

The method of the fourth aspect of the present invention is particularlyeffective at improving the performance of a modern diesel engine havinga high pressure fuel system.

Such diesel engines may be characterised in a number of ways.

Such engines are typically equipped with fuel injection equipmentmeeting or exceeding “Euro 5” emissions legislation or equivalentlegislation in US or other countries.

Such engines are typically equipped with fuel injectors having aplurality of apertures, each aperture having an inlet and an outlet.

Such engines may be characterised by apertures which are tapered suchthat the inlet diameter of the spray-holes is greater than the outletdiameter.

Such modern engines may be characterised by apertures having an outletdiameter of less than 500 μm, preferably less than 200 μm, morepreferably less than 150 μm, preferably less than 100 μm, mostpreferably less than 80 μm or less.

Such modern diesel engines may be characterised by apertures where aninner edge of the inlet is rounded.

Such modern diesel engines may be characterised by the injector havingmore than one aperture, suitably more than 2 apertures, preferably morethan 4 apertures, for example 6 or more apertures.

Such modern diesel engines may be characterised by an operating tiptemperature in excess of 250° C.

Such modern diesel engines may be characterised by a a fuel injectionsystem which provides a fuel pressure of more than 1350 bar, preferablymore than 1500 bar, more preferably more than 2000 bar. Preferably, thediesel engine has fuel injection system which comprises a common railinjection system.

The method of the present invention preferably improves the performanceof an engine having one or more of the above-described characteristics.

The method of the present invention improves the performance of anengine. This improvement in performance is suitably achieved by reducingdeposits in the engine.

The present invention may therefore provide a method of combatingdeposits in an engine comprising combusting in said engine a fuelcomposition of the fourth aspect.

The sixth aspect of the present invention preferably relates to a methodof combating deposits in an engine, preferably a diesel engine.Combating deposits may involve reducing or the preventing of theformation of deposits in an engine compared to when running the engineusing unadditised fuel. Such a method may be regarded as achieving “keepclean” performance.

Combating deposits may involve the removal of existing deposits in anengine. This may be regarded as achieving “clean up” performance.

In especially preferred embodiments the method of the sixth aspect ofthe present invention may be used to provide “keep clean” and “clean up”performance.

As explained above deposits may occur at different places within adiesel engine, for example a modern diesel engine.

The present invention is particularly useful in the prevention orreduction or removal of internal deposits in injectors of enginesoperating at high pressures and temperatures in which fuel may berecirculated and which comprise a plurality of fine apertures throughwhich the fuel is delivered to the engine. The present invention findsutility in engines for heavy duty vehicles and passenger vehicles.Passenger vehicles incorporating a high speed direct injection (or HSDI)engine may for example benefit from the present invention.

The present invention may also provide improved performance in moderndiesel engines having a high pressure fuel system by controllingexternal injector deposits, for example those occurring in the injectornozzle and/or at the injector tip. The ability to provide control ofinternal injector deposits and external injector deposits is a usefuladvantage of the present invention.

Suitably the present invention may reduce or prevent the formation ofexternal injector deposits. It may therefore provide “keep clean”performance in relation to external injector deposits.

Suitably the present invention may reduce or remove existing externalinjector deposits. It may therefore provide “clean up” performance inrelation to external injector deposits.

Suitably the present invention may reduce or prevent the formation ofinternal diesel injector deposits. It may therefore provide “keep clean”performance in relation to internal diesel injector deposits.

Suitably the present invention may reduce or remove existing internaldiesel injector deposits. It may therefore provide “clean up”performance in relation to internal diesel injector deposits.

The present invention may also combat deposits on vehicle fuel filters.This may include reducing or preventing the formation of deposits (“keepclean” performance) or the reduction or removal of existing deposits(“clean up” performance).

The diesel fuel compositions of the present invention may also provideimproved performance when used with traditional diesel engines.Preferably the improved performance is achieved when using the dieselfuel compositions in modern diesel engines having high pressure fuelsystems and when using the compositions in traditional diesel engines.This is important because it allows a single fuel to be provided thatcan be used in new engines and older vehicles.

The removal or reduction of IDIDs according to the present inventionwill lead to an improvement in performance of the engine.

The improvement in performance of the diesel engine system may bemeasured by a number of ways. Suitable methods will depend on the typeof engine and whether “keep clean” and/or “clean up” performance ismeasured.

An improvement in “keep clean” performance may be measured by comparisonwith a base fuel. “Clean up” performance can be observed by animprovement in performance of an already fouled engine.

The effectiveness of fuel additives is often assessed using a controlledengine test.

In Europe the Co-ordinating European Council for the development ofperformance tests for transportation fuels, lubricants and other fluids(the industry body known as CEC), has developed a test for additives formodern diesel engines such as HSDI engines. The CEC F-98-08 test is usedto assess whether diesel fuel is suitable for use in engines meeting newEuropean Union emissions regulations known as the “Euro 5” regulations.The test is based on a Peugeot DW10 engine using Euro 5 injectors, andis commonly referred to as DW10 test. This test measures power loss inthe engine due to deposits on the injectors, and is further described inexample 6.

Preferably the use of the fuel composition of the present inventionleads to reduced deposits in the DW10 test. For “keep clean” performancea reduction in the occurrence of deposits is preferably observed.

For “clean up” performance removal of deposits is preferably observed.The DW10 test is used to measure the power loss in modern diesel engineshaving a high pressure fuel system.

Suitably the use of a fuel composition of the present invention mayprovide a “keep clean” performance in modern diesel engines, that is theformation of deposits on the injectors of these engines may be inhibitedor prevented. Preferably this performance is such that a power loss ofless than 5%, preferably less than 2% is observed after 32 hours asmeasured by the DW10 test.

In some embodiments, the present invention may provide a power gain.Suitably when combusting a fuel composition according to the presentinvention a power gain in the DW10 test is observed compared to whencombusting an unadditised base fuel and with clean injectors. Suitably apower gain of at least 0.5%, preferably at least 1% is achieved within 4hours, preferably within 2 hours. Details of the methods used to measurethe power gain are given in example 8.

Suitably the use of a fuel composition of the present invention mayprovide a “clean up” performance in modern diesel engines that isdeposits on the injectors of an already fouled engine may be removed.Preferably this performance is such that the power of a fouled enginemay be returned to within 1% of the level achieved when using cleaninjectors within 16 hours, preferably 12 hours, more preferably 8 hoursas measured in the DW10 test.

Preferably rapid “clean-up” may be achieved in which the power isreturned to within 1% of the level observed using clean injectors within4 hours, preferably within 2 hours.

In some preferred embodiments, clean up may also provide a powerincrease. Thus a fouled engine may be treated to remove the existingdeposits and provide an additional power gain.

Clean injectors can include new injectors or injectors which have beenremoved and physically cleaned, for example in an ultrasound bath.

According to a seventh aspect of the present invention there the use ofan additive in a fuel composition to improve the performance of anengine combusting said fuel composition wherein the additive is aquaternary ammonium salt of formula:

wherein each of R¹ and R² is independently selected from an optionallysubstituted alkyl, alkenyl or aryl group having less than 8 carbonatoms, R together with N forms an aliphatic or aromatic group havingless than 12 carbon atoms and R⁵ is hydrogen or an optionallysubstituted hydrocarbyl group.

Preferred features of the seventh aspect of the present invention are asdefined in relation to the first, second, third and fifth aspects, andespecially as defined in relation to the sixth aspect.

The invention will now be further described with reference to thefollowing non-limiting examples. In the examples which follow the valuesgiven in parts per million (ppm) for treat rates denote active agentamount, not the amount of a formulation as added, and containing anactive agent. All parts per million are by weight.

EXAMPLE 1

Additive A19, Bis (1,1-dimethylpyrrolidin-1-ium) octadecenyl succinatewas prepared as follows:

A sample of octadenyl succinic acid was prepared by hydrolysis of axylene solution of a commercial sample of the corresponding anhydridebefore removing volatiles by rotary evaporation leaving a cream-colouredsolid. The acid value was determined, by wet analysis, to be 5.27 mMol/g(calc. 5.32).

N-methyl pyrrolidine (2.865 g, 33.7 mMol), dimethyl carbonate (12.298 g,136.6 mMol) and methanol (10 cm3) were charged to a tube and heated,with stirring, for one hour at 130° C., under autogeneous pressure. Theformation of a methyl carbonate salt was confirmed by FTIR(characteristic absorbance at 1651 cm⁻¹).

The solution of 1,1-dimethylpyrrolidin-1-ium methyl carbonate wastransferred to a round-bottom flask. Octadecenyl succinic acid (6.282 g,33.1 mMol of acidity) was added. On stirring and warming (oil bath, 45°C.) the solids dissolved, with gas evolution. After 60 minutes gasevolution had ceased. The solution was taken to dryness on a rotaryevaporator (2 mBar, 90° C.), forming orange-brown waxy solids which weredissolved, with warming, in an equal mass of 2-ethyl hexanol. Massbalances and FTIR spectra were in accord with substantially completeformation of a carboxylate salt (absorbances at about 1575 and 1378cm⁻¹)

EXAMPLE 2

Additive A21, Bis (N,N′-dimethyl imidazolium) octadecenyl succinate wasprepared as follows:

N-methyl imidazole (2.544 g, 31 mMol), dimethyl carbonate (10.96 g, 122mMol) and methanol (12.5 cm³) were charged to a tube and heated, withstirring, under autogeneous pressure, at 160° C. for three hours. Theformation of a methyl carbonate salt was confirmed by FTIR (absorbanceat 1645 cm⁻¹).

Material from the tube was transferred to a round-bottom flask andreacted with a single equivalent (acid value basis, 0.5 molarequivalents) of octadecenyl succinic acid, as set out above. Thematerial was stripped to dryness in the rotary evaporator (6 mBar, 90°C.). Mass balance was consistent with formation of the desired productin good yield. The material was dissolved, with strong heating, in anequal mass of 2-ethyl hexanol. The FTIR spectrum was consistent withformulation as the proposed carboxylate salt, with characteristicabsorbances at 1569 and 1379 cm⁻¹.

EXAMPLE 3

Additives A16, A17 and A18 were each prepared as a 50% w/w solution in2-ethyl hexanol as follows:

The succinic acid suspended in 2-ethylhexan-1-ol was placed in a boilingtube. One or two equivalents of cyclic tertiary amine and one or twoequivalents of epoxide were added and the reaction heated at 95° C. for6 hours. The product was confirmed via FTIR spectra.

The further compounds using the following acids, amines and epoxides:

Amine added Epoxide added Additive Acid (molar equiv) (molar equiv) A16Octadecenylsuccinic Methyl Pyrollidine 1,2-epoxybutane acid (2) (2) A17Octadecenylsuccinic Methyl Pyrollidine Iso propyl acid (2) glycidylether (2) A18 Octadecenylsuccinic Methyl Imidazole Iso propyl acid (2)glycidyl ether (2) A22 C30+ alpha Methyl Pyrollidine 1,2-epoxybutaneolefin succinic (1) (1) acid

The C30+ alpha olefin succinic acid is the reaction product of aterminal alkene consisting mainly of molecules having at least 30 carbonatoms and maleic anhydride. The alkene is available commercially fromChevron Phillips Chemical Company under the trade mark AlphaPlus® C30+.

EXAMPLE 4

Diesel fuel compositions were prepared comprising the additives listedin Table 1, added to aliquots all drawn from a common batch of RFO6 basefuel.

TABLE 1 Fuel Composition Additive (ppm active) Comparative C 105 1 A16105 2 A17 105 3 A18 105 4 A19 105 5 A21 105 6 A22 105

Additive C is a comparative low molecular weight succinimide detergentadditive, that was prepared as follows:

Polyisobutylene succinic anhydride with a Mn of 360((442g) was chargedto a reactor followed by solvent Shellso1150 (442g). 1 equivalent oftetraethylene pentamine (243g) was added and the mixture stirred at 175Cfor 3 hours whilst distilling off the water in a dean and starkcondenser. The product was then discharged from the reactor.

Table 2 below shows the specification for RFO6 base fuel.

TABLE 2 Limits Property Units Min Max Method Cetane Number 52.0 54.0 ENISO 5165 Density at 15° C. kg/m³ 833 837 EN ISO 3675 Distillation 50%v/v Point ° C. 245 — 95% v/v Point ° C. 345 350 FBP ° C. — 370 FlashPoint ° C. 55 — EN 22719 Cold Filter Plugging ° C. — −5 EN 116 PointViscosity at 40° C. mm²/sec 2.3 3.3 EN ISO 3104 Polycyclic Aromatic %m/m 3.0 6.0 IP 391 Hydrocarbons Sulphur Content mg/kg — 10 ASTM D 5453Copper Corrosion — 1 EN ISO 2160 Conradson Carbon % m/m — 0.2 EN ISO10370 Residue on 10% Dist. Residue Ash Content % m/m — 0.01 EN ISO 6245Water Content % m/m — 0.02 EN ISO 12937 Neutralisation mg — 0.02 ASTM D974 (Strong Acid) KOH/g Number Oxidation Stability mg/mL — 0.025 EN ISO12205 HFRR (WSD1,4) μm — 400 CEC F-06-A-96 Fatty Acid prohibited MethylEster

EXAMPLE 5

Each of the fuel compositions prepared in example 4 was tested using JetFuel Thermal Oxidation Test (JFTOT) equipment. In this test 800 ml offuel is flowed over an aluminium tube heated to 260° C. at a pressure ofapproximately 540 psi (3.72×10⁶ Pa). The test duration is 2.5 hours. Atthe end of test the aluminium tube is removed and the thickness ofdeposit compared to the comparative fuel.

The results are shown in table 2.

Deposit Fuel Thickness Composition (nm) Comparative 377 1 60 2 43 3 1054 49 5 43 6 21

EXAMPLE 6

The performance of fuel compositions of the present invention in moderndiesel engines having a high pressure fuel system may be testedaccording to the CECF-98-08 DW 10 method.

The engine of the injector fouling test is the PSA DW1OBTED4. Insummary, the engine characteristics are:

Design: Four cylinders in line, overhead camshaft, turbocharged with EGR

Capacity: 1998 cm³

Combustion chamber: Four valves, bowl in piston, wall guided directinjection

Power: 100 kW at 4000 rpm

Torque: 320 Nm at 2000 rpm

Injection system: Common rail with piezo electronically controlled6-hole injectors.

Max. pressure: 1600 bar (1.6×10⁸ Pa). Proprietary design by SIEMENS VDOEmissions control: Conforms with Euro IV limit values when combined withexhaust gas post-treatment system (DPF)

This engine was chosen as a design representative of the modern Europeanhigh-speed direct injection diesel engine capable of conforming topresent and future European emissions requirements. The common railinjection system uses a highly efficient nozzle design with roundedinlet edges and conical spray holes for optimal hydraulic flow. Thistype of nozzle, when combined with high fuel pressure has allowedadvances to be achieved in combustion efficiency, reduced noise andreduced fuel consumption, but are sensitive to influences that candisturb the fuel flow, such as deposit formation in the spray holes. Thepresence of these deposits causes a significant loss of engine power andincreased raw emissions.

The test is run with a future injector design representative ofanticipated Euro V injector technology.

It is considered necessary to establish a reliable baseline of injectorcondition before beginning fouling tests, so a sixteen hour running-inschedule for the test injectors is specified, using non-foulingreference fuel.

Full details of the CEC F-98-08 test method can be obtained from theCEC. The coking cycle is summarised below.

1. A warm up cycle (12 minutes) according to the following regime:

Duration Engine Speed Torque Step (minutes) (rpm) (Nm) 1 2 idle <5 2 32000 50 3 4 3500 75 4 3 4000 100

2. 8 hrs of engine operation consisting of 8 repeats of the followingcycle

Boost Air Duration Engine Speed Load Torque After IC Step (minutes)(rpm) (%) (Nm) (° C.) 1 2 1750 (20) 62 45 2 7 3000 (60) 173  50 3 2 1750(20) 62 45 4 7 3500 (80) 212  50 5 2 1750 (20) 62 45 6 10 4000 100  * 507 2 1250 (10) 20 43 8 7 3000 100  * 50 9 2 1250 (10) 20 43 10 10 2000100  * 50 11 2 1250 (10) 20 43 12 7 4000 100  * 50 * for expected rangesee CEC method CEC-F-98-08

3. Cool down to idle in 60 seconds and idle for 10 seconds

4. 4 hrs soak period

The standard CEC F-98-08 test method consists of 32 hours engineoperation corresponding to 4 repeats of steps 1-3 above, and 3 repeatsof step 4. ie 56 hours total test time excluding warm ups and cooldowns.

EXAMPLE 7

The effectiveness of the fuel compositions of the present invention inolder engine types may be assessed using a standard industry test—CECtest method No. CEC F-23-A-01.

This test measures injector nozzle coking using a Peugeot XUD9 A/LEngine and provides a means of discriminating between fuels of differentinjector nozzle coking propensity. Nozzle coking is the result of carbondeposits forming between the injector needle and the needle seat.Deposition of the carbon deposit is due to exposure of the injectorneedle and seat to combustion gases, potentially causing undesirablevariations in engine performance.

The Peugeot XUD9 A/L engine is a 4 cylinder indirect injection Dieselengine of 1.9 litre swept volume, obtained from Peugeot Citroen Motorsspecifically for the CEC PF023 method.

The test engine is fitted with cleaned injectors utilising unflattedinjector needles. The airflow at various needle lift positions have beenmeasured on a flow rig prior to test. The engine is operated for aperiod of 10 hours under cyclic conditions.

Time Speed Torque Stage (secs) (rpm) (Nm) 1 30 1200 ± 30 10 ± 2 2 603000 ± 30 50 ± 2 3 60 1300 ± 30 35 ± 2 4 120 1850 ± 30 50 ± 2

The propensity of the fuel to promote deposit formation on the fuelinjectors is determined by measuring the injector nozzle airflow againat the end of test, and comparing these values to those before test. Theresults are expressed in terms of percentage airflow reduction atvarious needle lift positions for all nozzles. The average value of theairflow reduction at 0.1 mm needle lift of all four nozzles is deemedthe level of injector coking for a given fuel.

EXAMPLE 8

In Europe the Co-ordinating European Council for the development ofperformance tests for transportation fuels, lubricants and other fluids(the industry body known as CEC), has developed a new test for additivesfor modern diesel engines such as HSDI engines. The CEC F-110-xx ¹ testis used to assess whether diesel fuel is suitable for use in enginesmeeting new European Union emissions regulations known as the “Euro 5”regulations. The test is based on a Peugeot DW10 engine using Euro 5injectors, and is commonly referred to as DW10C test. This test measuresthe effects of deposits on the injectors specific to IDID's with respectto injector sticking. Test procedure still in draft format and final CECissue number not yet available.

In this test thermocouples are positioned in the engine to enable theexhaust temperature of each cylinder to be measured. This, inconjunction with other measured parameters, allows injector sticking tobe tested.

The engine of the injector fouling test is the PSA DW10CTED4/E5. Insummary, the engine characteristics are:

Design: Four cylinders in line, overhead camshaft, turbocharged with EGR

Capacity: 1997 cm³

Combustion chamber: Four valves, bowl in piston, wall guided directinjection

Power: 120 kW at 3750 rpm

Torque: 340 Nm at 2000 rpm

Injection system: Common rail with piezo electronically controlled6-hole injectors.

Max. pressure: 1600 bar (1.6×10⁸ Pa). Proprietary design by Delphi

Emissions control: Conforms with Euro V limit values when combined withexhaust gas post-treatment system (DPF)

This engine was chosen as a design representative of the modern Europeanhigh-speed direct injection diesel engine capable of conforming topresent and future European emissions requirements. The common railinjection system uses a highly efficient nozzle design with roundedinlet edges and conical spray holes for optimal hydraulic flow. Thistype of nozzle, when combined with high fuel pressure has allowedadvances to be achieved in combustion efficiency, reduced noise andreduced fuel consumption, but are sensitive to influences that can causeinjector sticking.

The test is run with current injector design conforming to Euro Vinjector technology.

Full details of the CEC F-110-xx test method can be obtained from theCEC. The test cycle is summarised below.

1. Warm-Up stages:

Duration Engine Speed Torque Step (minutes) (rpm) (Nm) 1 2 1000 10 2 32000 50 3 4 3500 75 4 3 3750 100

2. Main Run

Duration Engine Speed Torque Step (seconds) (rpm) (Nm) 1 1470 1750 2801 - Ramp → 2 270 3000 — 2 - Ramp → 1 30 — —

The test procedure consists of alternating sequences of soak periodsfollowed by cold starts preceding main run cycles of engine operation.There are 5 main runs and 6 cold starts.

If the engine should fail to start or stall during engine operation andcannot be restarted the test is aborted.

During the test ECU parameters are recorded together with exhausttemperatures to evaluate any indication of injector sticking. Theseparameters contribute to an overall demerit rating at the conclusion ofthe test.

1. A quaternary ammonium salt of formula:

wherein each of R¹ and R² is independently selected from an optionallysubstituted alkyl, alkenyl or aryl group having less than 8 carbonatoms, R together with N forms an aliphatic or aromatic heterocyclehaving less than 12 carbon atoms and R⁵ is hydrogen or an optionallysubstituted hydrocarbyl group.
 2. The quaternary ammonium salt accordingto claim 1 which is prepared by reacting a cyclic tertiary amine offormula R══NR¹ with a quaternising agent selected from: (i) an ester offormula R⁵COOR²; (ii) a carbonate compound of formula R⁴OCOOR² and thena carboxylic acid of formula R⁵COOH; and (iii) an epoxide having lessthan 8 carbon atoms and a carboxylic acid of formula R⁵COOH; wherein R⁴is an optionally substituted hydrocarbyl group.
 3. The quaternaryammonium salt according to claim 2 wherein the quaternising agent is(ii) a carbonate compound of formula R⁴OCOOR² and then a carboxylic acidof formula R⁵COOH.
 4. A quaternary ammonium salt which is the reactionproduct of: (a) a cyclic tertiary amine having less than 19 carbonatoms; (b) an epoxide having less than 8 carbon atoms; and (c) acarboxylic acid of formula R⁵COOH; wherein R⁵ is hydrogen or anoptionally substituted hydrocarbyl group.
 5. A method of preparing aquaternary ammonium salt, the method comprising reacting (a) a cyclictertiary amine having less than 19 carbon atoms with (b) an epoxide inthe presence of (c) a carboxylic acid of formula R⁵COOH; wherein R⁵ ishydrogen or an optionally substituted hydrocarbyl group.
 6. The methodaccording to claim 5 wherein component (a) comprises an amine of formulaR══NR¹ in which R¹ is an optionally substituted hydrocarbyl group and Rand N together form a heterocycle having less than 12 carbon atoms. 7.An additive composition comprising one or more quaternary ammonium.compounds according to claim 1 and a diluent or carrier.
 8. Alubricating composition comprising as an additive one or more quaternaryammonium compounds according to claim 1 and a lubricant.
 9. A fuelcomposition comprising as an additive one or more quaternary ammoniumcompounds according to claim 1 and a fuel.
 10. The fuel compositionaccording to claim 9 wherein the fuel is diesel fuel,
 11. The fuelcomposition according to claim 10 which comprises one or more furtherdetergents selected from the group consisting of: (i) an additionalquaternary ammonium salt additive which is not a quatemary ammoniumcompound of claim 1; (ii) the product of a Mannich reaction between analdehyde, an amine and an optionally substituted phenol; (iii) thereaction product of a carboxylic acid-derived acylating agent and anamine; (iv) the reaction product of a carboxylic acid-derived acylatingagent and hydrazine; (v) a salt formed by the reaction of acarboxylic-acid with di-n-butylamine or tri-n-butylamine; (vi) thereaction product of a hydrocarbyl-substituted &carboxylic-acid oranhydride and an amine compound or salt which product comprises at leastone amino triazole group; and (vii) a substituted polyaromatic detergentadditive.
 12. The fuel composition according to claim 9 wherein the fuelis gasoline fuel.
 13. The fuel composition according to claim 12 whichcomprises one or more gasoline detergents selected from the groupconsisting of: (p) hydrocarbyl-substituted polyoxyalkylene amines orpolyetheramines; (q) acylated nitrogen compounds which are the reactionproduct of a carboxylic acid-derived acylating agent and an amine; (r)hydrocarbyl-substituted amines wherein the hydrocarbyl substituent issubstantially aliphatic and contains at least 8 carbon atoms; (s)Mannich base additives comprising nitrogen-containing condensates of aphenol, aldehyde and primary or secondary amine; (t) aromatic esters ofa polyalkylphenoxyalkanol; (u) an additional quaternary ammonium saltadditive which is not a quaternary ammonium compound of claim 1; and (v)tertiary hydrocarbyl amines having a maximum of 30 carbon atoms.
 14. Amethod of preparing a fuel composition according to claim 9, the methodcomprising adding the quaternary ammonium salt additive to the fuelafter the fuel has left the distribution terminal.
 15. A method ofimproving the performance of an engine, the method comprising combustingin said engine a fuel composition comprising as an additive one or morequaternary ammonium compounds according to claim
 1. 16. The methodaccording to claim 15 wherein the engine is a gasoline engine and thefuel is a gasoline fuel.
 17. The method according to claim 15 whereinthe engine is a diesel engine having a fuel injection system whichcomprises a high pressure fuel injection (H H) system with fuelpressures greater than 1350 bar.
 18. The method according to claim 17wherein improvement in performance is achieved by combating deposits inthe engine,
 19. The method according to claim 18 which combats internaldiesel injector deposits.
 20. The method according to claim 18 whichcombats external diesel injector deposits, including injector nozzledeposits and injector tip deposits,
 21. The method according to claim 18which combats fuel filter deposits.
 22. The method according to claim 17wherein the improvement in performance is a power gain compared to whencombusting an unadditised base fuel and with clean injectors. 23.(canceled)
 24. The method according to claim 15 to achieve “keep clean”performance.
 25. The method according to claim 15 to achieve “clean up”performance.
 26. The method according to claim 15 wherein theimprovement in performance is achieved by combating deposits in theengine.
 27. The method according to claim 15 wherein the improvement inperformance is a power gain compared to when combusting an unadditizedbase fuel and with clean injectors.